Fact-checked by Grok 2 weeks ago

PECOTA

PECOTA, an acronym for Player Empirical Comparison and Optimization Test Algorithm, is a sabermetric projection system developed by statistician Nate Silver in 2003 to forecast Major League Baseball player performance and team outcomes.^[1] It operates by identifying historical "comparable" players with similar career trajectories and statistical profiles, then generating projections based on weighted past performances, with greater emphasis on recent seasons and adjustments for factors like age and playing time.^[1] Originally created for Baseball Prospectus, where Silver served as lead prospector until 2009, PECOTA has since been maintained and refined by the organization's analytics team, evolving into one of the most accurate and influential tools in baseball forecasting.^[2]^[3] The system's methodology begins with a baseline calculation from a player's historical data, incorporating regression to the mean and empirical comparisons to thousands of past player-seasons to predict individual events such as hits, home runs, strikeouts, and walks.^[1] These player-level projections are then aggregated using depth charts—often updated with human input—to estimate team runs scored and allowed, ultimately yielding win-loss predictions and playoff probabilities.^[2] Unlike simpler systems that rely solely on weighted averages, PECOTA's use of comparables allows it to account for platoon splits, ballpark effects, and injury risks, making it particularly effective for evaluating prospects and mid-career players.^[3] Since its inception, PECOTA has gained prominence in the sabermetrics community for its predictive accuracy, regarded as one of the most accurate projection systems in the industry.^[1] Annual releases, such as the 2025 edition, provide percentile-based forecasts accessible via spreadsheets, supporting fantasy baseball, scouting, and front-office decisions across MLB.^[3] While Silver's departure from Baseball Prospectus in 2009 to focus on FiveThirtyEight, which he had founded the previous year, marked a transition for the system, ongoing tweaks ensure its relevance in an era of expanding baseball analytics.^[2]

History and Development

Origins and Creation

PECOTA, an acronym for Player Empirical Comparison and Optimization Test Algorithm, originated as a backronym honoring Bill Pecota, a journeyman Major League Baseball infielder known for his .249 career batting average.^[1] The system was developed by Nate Silver in the early 2000s while he worked as a consultant at KPMG, initially as a personal project to advance baseball forecasting beyond basic averages of past performance.^[4] Silver created PECOTA to address limitations in traditional projections by incorporating player variability and career trajectories, drawing foundational influences from sabermetric pioneers such as Bill James, whose concepts of player similarity scores and archetypes informed the approach of matching current players to historical comparables.^[5] Silver sold PECOTA to Baseball Prospectus in 2003, where it was integrated as their proprietary projection tool to provide more nuanced forecasts for player performance, emphasizing probabilistic outcomes over deterministic estimates.^[4] The system's first public release occurred that year through the Baseball Prospectus 2003 annual book and premium subscription content on their website, marking its debut in sabermetric analysis.^[6]

Key Milestones and Revisions

PECOTA's first widespread release occurred in 2003, when it was integrated into Baseball Prospectus as part of the site's subscription model, marking its transition from an internal tool to a publicly available projection system.^[7] In 2009, creator Nate Silver departed Baseball Prospectus to pursue other projects, leading to a transitional period where the system was maintained and updated by the site's team, including interim projections produced using the original spreadsheet methodology.^[8] Throughout the 2010s, PECOTA underwent significant revisions, including the reintroduction of a more robust computational process in 2010 that expanded coverage to over twice as many players and integrated it with Baseball Prospectus's database for ongoing updates.^[7]^[9] By 2011, methodological tweaks adapted PECOTA to the site's new Wins Above Replacement Player (WARP) framework.^[10] A notable 2021 update introduced information-based adjustments for in-season projections, employing a Bayesian approach to blend preseason PECOTA forecasts with actual performance data, thereby providing more dynamic rest-of-season estimates tailored to individual player uncertainty.^[11] In 2025, Baseball Prospectus announced major enhancements to PECOTA's pitcher projections, including improved rookie forecasting through integration of advanced pitch metrics like StuffPro, resulting in reduced projection errors by hundreds of runs overall as demonstrated in back-testing against prior seasons.^[12]

Methodology

Comparable Players

The core of PECOTA's projection system lies in its comparable players algorithm, which identifies historical analogs to forecast a current player's future performance. The process begins by matching the target player against a comprehensive database of major league player-seasons dating back to the 1950s. Matches are filtered initially by key demographic and physical factors, including the player's age, body type (such as height and weight), handedness, and primary position, to ensure relevance in career trajectory and physical demands.^[9]^[13]^[14] Once filtered, PECOTA calculates similarity scores for potential comparables using a multi-dimensional Euclidean distance metric across a vector of performance peripherals, such as contact rate, power output, speed, and plate discipline metrics for hitters, or strikeout rate, ground-ball tendency, and walk rate for pitchers. This distance is computed in a high-dimensional statistical space, where closer distances indicate greater similarity, allowing the system to rank the top 100 most analogous historical players. The algorithm prioritizes peripherals over raw outcomes to capture underlying skills less affected by external variables like ballpark effects or luck.^[15]^[16]^[17] These comparables form a "neighborhood" around the target player, rather than a simple average of stats, with weights assigned based on recency of the historical seasons and alignment in career stage to emphasize patterns from more contemporary and developmentally similar contexts. For instance, projecting a 25-year-old outfielder with strong power and speed might yield comparables like a young Ken Griffey Jr., drawn from players exhibiting similar power-speed combinations in their mid-20s. This weighted neighborhood avoids over-reliance on outliers and provides a robust foundation for subsequent probabilistic modeling.^[13]^[18]^[15]

Peripheral Statistics and Adjustments

PECOTA incorporates a range of peripheral statistics beyond traditional counting stats to capture underlying skills and tendencies that influence player performance. These include contact rate (derived as one minus the strikeout rate), walk rate, strikeout rate, groundball-to-flyball ratios, platoon splits (differences in performance against left- and right-handed opponents), and usage metrics such as pitches seen per plate appearance. For hitters, these peripherals help estimate components of overall production like True Average (TAv), while for pitchers, they inform estimators such as Fielding Independent Pitching (FIP) by focusing on the "three true outcomes"—walks, strikeouts, and home runs—while assuming league-average outcomes on balls in play.^[19]^[20] To enable fair comparisons across players and seasons, PECOTA normalizes these peripheral statistics for contextual factors. Adjustments account for era-specific differences, such as varying league-wide strikeout and walk rates between the dead-ball era and the steroid era, by scaling raw stats relative to league averages from the player's historical context. Park factors are applied to adjust for venue-specific effects, like how Coors Field inflates flyball distances or how hitter-friendly parks boost home run rates; this involves multiplying the raw peripheral by a park adjustment multiplier derived from multi-year data on run scoring and batted-ball outcomes in that stadium. A basic form of such normalization can be expressed as:

\text{adjusted stat} = \text{raw stat} \times \left( \frac{\text{current league average}}{\text{player's era average}} \right) \times \text{park factor}

This ensures peripherals from different eras and parks are comparable before matching to similar players.^[21]^[22] Injury and aging adjustments further refine these normalized peripherals to project availability and skill trajectory. PECOTA estimates injury risk through an Attrition Rate, which calculates the probability of a player experiencing at least a 50% drop in playing time based on historical patterns among comparable players, incorporating past playing time history and, where available, medical data on injury severity. For aging, it applies customized curves derived from the career paths of matched comparables, rather than generic league-wide declines; for instance, a young power hitter's home run rate might be adjusted upward if comparables typically peaked in their late 20s, while strikeout rates for pitchers are regressed toward increasing vulnerability with age. These adjustments are iterated within regressions on the comparable set to align projected peripherals with baseline performance metrics like TAv or ERA.^[22]^[23]

Probability Distributions

PECOTA generates probabilistic forecasts by aggregating the historical performances of matched comparable players into a multivariate probability distribution, capturing the range of potential outcomes for key statistics such as on-base plus slugging (OPS), home runs (HR), batting average (BA), and earned run average (ERA). This approach emphasizes the inherent variability in player performance rather than relying solely on point estimates, drawing from the career trajectories of similar players to model future possibilities. The system identifies comparable players based on factors like age, body type, position, and statistical similarity, then weights their past seasons—prioritizing more recent and closely matched ones—to form the basis of the distribution.^[13]^[23] To construct these distributions, PECOTA employs a two-stage process: first, it creates a baseline forecast from the player's own historical data, adjusted via a custom aging curve derived from the comparables' trajectories; second, it fits the aggregated data into a distribution that reflects correlations across multiple stats, such as the relationship between singles and extra-base hits for hitters, often using a categorical distribution framework to model batting events more accurately than simple multinomial assumptions. For pitchers, similar aggregation focuses on metrics like ERA, incorporating deviations observed in comparable pitchers' seasons. The resulting multivariate distribution allows for joint modeling of stats, avoiding unrealistic independence assumptions. While specific fitting techniques vary by iteration, a common representation is the player's projected statistic following a normal distribution centered on the weighted mean of the comparables' performances, with variance estimated from historical deviations among those players:

\text{Projected Stat} \sim \mathcal{N}(\mu_w, \sigma_h^2)

where \mu_w is the weighted mean from comparables, and \sigma_h^2 captures the spread of historical outcomes.^[23]^[24]^[11] Handling uncertainty is central to PECOTA's distributions, incorporating regression to the mean to temper extreme past performances and simulating thousands of hypothetical seasons to generate full outcome probabilities. This simulation accounts for factors like playing time variability, injury risk, and sample size effects—such as wider spreads for players with limited prior data—ensuring the distributions reflect realistic downside risks (e.g., attrition) and upside potential (e.g., breakouts). For instance, variance decreases as projected plate appearances (PA) or innings pitched (IP) increase, narrowing the distribution for established players. Team and contextual factors, like ballpark effects or lineup position, serve as post hoc modifiers to these individual distributions without altering the core aggregation.^[23]^[13]^[24] The primary outputs from these distributions are percentile forecasts, providing 10th to 90th percentile ranges (or expanded to 1st to 99th in recent versions) alongside the median (weighted mean) for each stat, enabling users to assess likely floors, ceilings, and tails of performance. For hitters with 300+ PA, the 80th percentile might show a 63.5% deviation above the mean in true average (TAv), while pitchers with 70+ IP could see a 50.5% upside in ERA-adjusted metrics; these ranges highlight asymmetry, with greater downside variance for volatile players like prospects. By publishing these percentiles, PECOTA offers a comprehensive view of uncertainty, distinguishing it from systems focused only on expected values.^[23]^[24]^[13]

Recent Methodological Updates

As of the 2025 edition, PECOTA has incorporated advanced metrics to enhance projection accuracy. For pitchers, the system now integrates StuffPro, a metric evaluating pitch quality and movement, to better project balls in play and apportion run values to specific batting outcomes using a multinomial model based on the pitcher's tendencies. Batter projections continue to evolve with adjustments for the current run environment and participation rates. These updates build on the foundational comparable-based approach while adapting to modern analytics like exit velocity and launch angle data.^[12]

Team and Contextual Factors

PECOTA incorporates park effects to normalize player performance data across different ballparks, mitigating biases introduced by venue-specific characteristics such as dimensions, altitude, and weather. For instance, Coors Field's high altitude inflates offensive output due to reduced air density, leading to more home runs and higher run totals; PECOTA adjusts historical and projected statistics accordingly to estimate a player's true talent independent of home environment. These adjustments are derived from multi-year park factors calculated by comparing home and road performance league-wide, ensuring projections reflect neutral conditions before applying team-specific contexts.^[25] In terms of team context, PECOTA accounts for elements like lineup quality, bullpen support, and defensive efficiency that influence individual outcomes. For pitchers, projected earned run averages (ERAs) are modified based on team defense metrics, such as Fielding Runs Above Average (FRAA), which quantifies defensive contributions by position and batted ball type to isolate pitching skill from fielding support. Bullpen support is handled through support-neutral value added (SNVA), separating a starter's performance from relief pitching quality—negative pen support indicates a strong bullpen that lowers the starter's ERA beyond their peripherals, while the reverse inflates it. Lineup quality affects hitters via adjustments to run production and baserunner advancement, drawing from team-wide run environment and opportunity metrics to simulate realistic scoring contexts.^[22]^[26] Positional scarcity is addressed implicitly through replacement-level benchmarks tailored to each position, recognizing varying talent availability and defensive demands. Catchers and shortstops, for example, face higher replacement thresholds due to skill scarcity and physical toll, whereas first basemen have lower ones; PECOTA's value over replacement player (VORP) metric benchmarks projections against these position-specific floors, where a full team of replacements is calibrated to win approximately 48-50 games. This ensures valuations capture the marginal value of players at scarce positions without over- or understating contributions.^[27] Interaction modeling in PECOTA simulates player-team synergies by integrating contextual modifiers into probability distributions, such as adjusting a pitcher's ERA for projected team defense or a hitter's RBI opportunities based on lineup composition. These interactions are modeled through regressions on comparable player data, incorporating team-level inputs like defensive efficiency and offensive support to forecast interdependent outcomes, though the system emphasizes individual baselines modulated by ensemble effects rather than complex pairwise simulations.^[22]

Projection Outputs and Applications

Individual Player Forecasts

PECOTA generates detailed forecasts for individual players, covering both traditional and advanced performance metrics tailored to hitters and pitchers. For hitters, projections include standard fantasy baseball categories such as batting average (AVG), home runs (HR), runs batted in (RBI), and stolen bases (SB), derived from modeled rates of singles, doubles, triples, walks, and strikeouts. Advanced metrics like weighted on-base average (wOBA) and weighted runs created plus (wRC+) are also forecasted, providing a more comprehensive view of offensive value independent of ballpark and league effects. Pitcher projections similarly encompass earned run average (ERA), walks plus hits per inning pitched (WHIP), strikeouts (K), and wins (W), with advanced indicators such as fielding independent pitching (FIP) to isolate pitcher-controlled outcomes like home runs allowed, walks, and strikeouts. These outputs stem from the system's comparable player matching and probability distributions, adjusted for current run environments.^[12]^[28] Playing time estimates form a critical component of individual forecasts, projecting plate appearances (PA) for hitters and innings pitched (IP) for pitchers based on historical usage patterns, roster depth, and injury risk factors. These are informed by manual depth chart allocations that distribute playing time shares across positions, incorporating team needs and player durability. For instance, a veteran with injury history might see reduced PA projections compared to a healthy prime-age player, reflecting realistic opportunities rather than full-season assumptions. Injury risk is modeled probabilistically, often leading to conservative estimates for players over 30 or those with recent medical issues.^[29]^[30] Forecasts incorporate career arc modeling through age-specific adjustments, using trajectories from comparable historical players to simulate peak performance, plateau, and decline phases. Younger players, typically around age 27, receive upward adjustments anticipating skill maturation, while those aged 35 and older face downward tweaks for expected physical decline in power, speed, and durability. This approach ensures projections align with empirical aging patterns, such as peak offensive output in the late 20s followed by gradual erosion.^[17] To convey uncertainty, PECOTA outputs projections across multiple percentiles rather than a single point estimate, offering a distribution of possible outcomes with associated confidence levels. The 50th percentile represents the median expectation, while 10th and 90th percentiles capture downside and upside risks, respectively. This percentile-based format, updated annually, allows users to assess variance influenced by factors like health and role stability.^[24]

Team and League Projections

PECOTA aggregates individual player projections to generate team-level forecasts by summing projected performance metrics across a team's roster, incorporating assumptions about playing time, rotations, and lineups based on depth charts. This process begins with player-specific outputs, such as batting events for hitters and pitching outcomes for pitchers, which are combined to estimate total team runs scored and allowed. For instance, offensive projections are totaled by position and lineup slot, while pitching projections account for starter and reliever roles, ensuring a comprehensive team statistical profile.^[12]^[31] To translate these aggregated statistics into win-loss estimates, PECOTA applies the Pythagorean expectation formula, which calculates expected winning percentage as the ratio of runs scored squared to the sum of runs scored squared and runs allowed squared, adjusted for the league's run environment. This method introduces variance to account for elements of luck and sequencing, providing a distribution of possible outcomes rather than a single point estimate. Team win totals are thus derived from these expected runs, with further refinements for park factors and schedule strength to maintain realism.^[12]^[32] League-wide projections emerge from the summation of all team forecasts, establishing baseline offensive and defensive levels across the majors. PECOTA adjusts these for anticipated changes, such as rule modifications like the 2023 pitch clock, which influenced run-scoring environments by increasing pace and reducing dead time, thereby elevating projected league totals in subsequent years. This holistic view ensures that individual team projections align with overall league balance, preventing imbalances in total wins or runs.^[12] Depth and injury effects are simulated through Monte Carlo methods, running thousands of season iterations to model roster variability, including player absences and replacements from minor leagues or bench options. These simulations incorporate probabilistic injury rates based on historical data and position-specific risks, yielding a range of team performance outcomes that reflect real-world uncertainties. By averaging across these runs, PECOTA produces robust team and league projections that capture both central tendencies and potential deviations.^[12]^[32]

Usage in Fantasy and Analytics

PECOTA projections are integral to fantasy baseball, providing forecasts for standard categories such as batting average, home runs, RBIs, stolen bases, ERA, WHIP, and strikeouts, which align with both roto and points-league formats. Baseball Prospectus utilizes these outputs to develop specialized tools like The AX, a PECOTA-driven auction calculator that generates customized player valuations and rankings for draft preparation across various league settings.^[33] This integration enables fantasy participants to simulate outcomes and optimize rosters based on probabilistic distributions derived from historical comparables.^[34] In professional baseball operations, PECOTA informs front-office strategies through detailed reports from Baseball Prospectus, influencing evaluations of player contracts, trade acquisitions, and roster constructions by quantifying expected value and risk.^[2] For instance, teams reference PECOTA's percentile-based forecasts to assess long-term contributions, such as projecting surplus value in arbitration-eligible players or free-agent signings.^[35] These applications extend to broader analytics, where the system's emphasis on similar-player matching aids in scenario planning for team performance. PECOTA holds a prominent role in sabermetric discourse and media coverage, frequently cited in analyses of player potential and league trends due to its rigorous empirical foundation.^[36] Annual releases of PECOTA standings often ignite debates among analysts and fans, as seen in discussions questioning projections for contenders like the Chicago Cubs.^[37] Such engagements highlight its influence in shaping narratives around strategic decisions and performance expectations. Despite its strengths, PECOTA's preseason-oriented design imposes limitations for dynamic applications, as it does not incorporate real-time data like injuries or midseason trades, necessitating user interpretation to adapt forecasts for waiver wire pickups or in-season adjustments.^[38] This static nature underscores the need for complementary tools in ongoing analytics workflows.^[39]

Comparisons and Alternatives

Major Competing Systems

One prominent alternative to PECOTA is the ZiPS projection system, developed by Dan Szymborski. ZiPS employs a regression-based approach that weights averages from up to four years of performance data, incorporating minor league statistics where available to enhance projections for prospects and players with limited major league experience. It adjusts for aging through comparisons to similar historical players and emphasizes rapid in-season updates, allowing for daily revisions based on recent performance trends.^[40]^[41] Another widely used system is Steamer, created by Jared Cross, Dash Davidson, and Peter Rosenbloom. Steamer functions as a hybrid model that regresses recent performance—primarily from the past three seasons—toward league means, using age-adjusted patterns and player similarity metrics derived from multiple statistical categories to forecast outcomes. It particularly excels in estimating playing time by blending statistical inputs with positional depth considerations, making it a staple for fantasy baseball applications.^[42] The Marcel system, devised by Tom Tango, serves as a straightforward baseline projection tool. It calculates weighted averages of a player's major league statistics from the previous three seasons, with heavier emphasis on more recent years, while applying regression to the mean and basic age adjustments. Valued for its simplicity and transparency, Marcel avoids complex inputs like minor league data, enabling quick computations and providing a benchmark for more elaborate systems.^[40] Among ensemble methods, the ATC projections by Ariel Cohen aggregate outputs from multiple systems such as ZiPS and Steamer, assigning weights based on each source's historical accuracy for specific statistics. This weighted averaging, supplemented by manual adjustments for playing time, aims to leverage collective strengths while mitigating individual biases. Similarly, FanGraphs' Fans projections rely on crowdsourced inputs from users, averaging community-submitted estimates to capture collective wisdom, often resulting in optimistic forecasts particularly for playing time and emerging talents.^[43]^[40]

Key Differences and Strengths

PECOTA distinguishes itself through its use of comparable players to model career trajectories and archetypes, drawing on historical data to identify similar players based on factors such as age, body type, position, and performance metrics like contact rates and power.^[13]^[1] This approach enables more nuanced projections for players with limited major league experience, particularly prospects, by incorporating minor league performance levels into comparable selection and enhancing rookie pitcher accuracy through advanced metrics like StuffPro.^[12]^[44] In contrast to simpler systems like Marcel, which relies on a basic weighted average of a player's last three seasons regressed toward league averages without historical comparisons, PECOTA introduces greater complexity by integrating full career arcs from comparable players, aiming for higher fidelity in forecasting development paths and positional adjustments.^[13]^[40] Compared to Steamer, which emphasizes recent-season weighting and regression without explicit historical depth, PECOTA prioritizes long-term patterns from similar archetypes, reducing potential recency bias in projections for evolving players.^[13] While PECOTA's proprietary methodology offers these advantages, it also presents trade-offs, including less transparency than open-source alternatives like Marcel or Steamer, which can limit accessibility and real-time adjustments.^[13] Additionally, its computational intensity from comparable matching contributes to higher demands, though a simplified version has shown comparable effectiveness to baseline systems.^[40] PECOTA is frequently incorporated into ensemble projections, blending with systems like ZiPS and Steamer to leverage collective strengths for more robust forecasts in fantasy baseball and analytics applications.^[45]

Accuracy and Evaluation

Assessment Methods

PECOTA's accuracy is evaluated using a combination of error metrics tailored to its point estimates and probabilistic distributions. For individual player statistics, such as batting average or ERA, the primary metric is Mean Absolute Error (MAE), which calculates the average absolute difference between projected and actual values, often weighted by plate appearances (PA) for hitters or innings pitched (IP) for pitchers to account for playing time variability.^[46] Root Mean Square Error (RMSE) is employed for assessing the overall distribution of outcomes, as it penalizes larger deviations more heavily and provides insight into the spread of projections around actual performance.^[47] For PECOTA's probabilistic components, such as percentile-based forecasts or success likelihoods, log-likelihood scores measure how well the projected probability distributions align with observed outcomes, rewarding well-calibrated predictions that assign higher probabilities to likely events.^[48] Benchmarks for PECOTA involve comparisons to baseline projections, including naive methods like repeating a player's previous season statistics, which serve as a simple reference for improvement, and aggregated systems available on platforms like FanGraphs that blend multiple models for robustness.^[46] These comparisons often rank PECOTA against competitors such as ZiPS, Steamer, and Marcel across categories like OPS for hitters and ERA for pitchers, using metrics like MAE and correlation coefficients to quantify relative performance.^[47] Validation approaches emphasize out-of-sample testing, where projections for prior seasons are generated and compared to actual results from holdout years to simulate real-world forecasting without overfitting to known data.^[48] Evaluations are conducted separately for hitters and pitchers, with minimum thresholds such as 300 PA or 130 IP to ensure sufficient sample sizes for reliable comparisons, focusing on key outcomes like weighted on-base average (wOBA) for hitters.^[46] Actual performance data for these assessments is sourced from comprehensive baseball databases, including Retrosheet for play-by-play details and Baseball-Reference for aggregated seasonal statistics, enabling precise matching of projected versus realized metrics.^[49] FanGraphs also provides processed data for broader league-level validations.^[48]

Historical Performance and Improvements

In its early years before 2010, PECOTA demonstrated particular strength in projecting hitter performance, tying for the best root mean square error (RMSE) of 0.030 in batting average among major systems and achieving an RMSE of 0.069 in on-base plus slugging (OPS). It also excelled in forecasting counting stats like runs scored, RBIs, and stolen bases, benefiting from integrated depth chart projections for playing time. However, the system underestimated pitcher volatility, posting a higher ERA RMSE of 1.17 and strikeout RMSE of 33.6 compared to competitors, which highlighted challenges in capturing the variability of pitching outcomes.^[50] During the 2010s, PECOTA evolved into a top-tier projection system through iterative refinements, consistently ranking competitively in annual reviews despite occasional variability. For instance, in evaluations of 2015 projections, it placed mid-pack for overall hitter accuracy (e.g., wOBA+ RMSE of 0.104) and pitcher metrics (e.g., ERA+ RMSE of 0.221), trailing leaders like Steamer but often matching or exceeding baselines like Marcel. Post-2015 enhancements incorporated advanced batted-ball data akin to Statcast metrics, contributing to improved forecasts; one study combined PECOTA outputs with Statcast-derived predictions via linear regression to boost batting average accuracy beyond standalone PECOTA results. These updates helped PECOTA achieve stronger rankings in subsequent seasons, particularly for elite performers.^[51]^[52]^[53] Back-testing of the 2024 season using data through 2023 showed that refinements improved projection accuracy by over 341 total runs overall, with batter projections demonstrating strong performance relative to baselines. However, in team win projections for 2024, PECOTA ranked behind ZiPS and FanGraphs according to Mahalanobis distance metrics (D1=70.5 for PECOTA vs. 56.2 for ZiPS).^[12]^[54] For 2025, the system introduced targeted upgrades to pitcher projections, integrating StuffPro metrics for balls-in-play and run environment adjustments; preseason back-testing indicated potential enhancements of hundreds of runs overall, including over 113 runs for rookies, to address longstanding weaknesses in novice pitcher forecasts. As of November 2025, comprehensive post-season evaluations of the 2025 projections' actual accuracy have not been widely published.^[12]^[55] Over time, PECOTA has exhibited consistent outperformance in home run and ERA projections, with low error rates for high-impact pitchers (e.g., ERA+ RMSE of 0.133 for WAR >4.0 talents in 2015 reviews) and reliable power forecasts tied to its similarity-based modeling. Ongoing refinements to aging curves, including curve-fitting processes to smooth progressions and mitigate selection bias in adjacent-season comparisons, have reduced projection biases, ensuring more orderly performance trajectories across player careers.^[52]^[56]

References

[1]
Player Empirical Comparison and Optimization Test Algorithm ...
PECOTA is Baseball Prospectus' system for projecting player performance, using historical comparisons of players with similar career paths.
[2]
What is PECOTA, and should you hate it? - ESPN
Feb 7, 2017 · Player Empirical Comparison and Optimization Test Algorithm, or PECOTA, is the projection system created by Nate Silver for Baseball Prospectus in the early ...
[3]
PECOTA Projections | Baseball Prospectus
PECOTA is a system that projects player and team performance using past performance to predict the most likely outcome for the following season.
[4]
Nate Silver - The University of Chicago Magazine
Silver, AB'00, is the managing partner of Baseball Prospectus (BP). It's a think tank devoted to the statistical analysis of the sport, or sabermetrics—a term ...
[5]
An Unfiltered Interview with Nate Silver - The Baseball Analysts
Feb 12, 2007 · Baseball Prospectus was looking for a new projection system in anticipation of launching its premium service and purchased PECOTA from Nate in ...<|control11|><|separator|>
[6]
The BP Wayback Machine: 2003 PECOTA Preview
Feb 8, 2013 · It's been a decade since the first time PECOTA projected team performance at BP in the piece reprinted below, which was originally published on ...
[7]
Reintroducing PECOTA: What A Long, Strange Trip It Has Been
Sep 27, 2010 · The original PECOTA process, as long-time readers know, was designed by Nate Silver and first offered at Baseball Prospectus when we went to a ...Missing: origins | Show results with:origins
[8]
State of the Prospectus: Spring 2009
Mar 24, 2009 · –Nate Silver Chicago, IL March 22, 2009. As part of Nate's stepping back and my stepping forward into the Managing Partner role, I was asked ...Missing: departure | Show results with:departure
[9]
Reintroducing PECOTA: They're Here! - Baseball Prospectus
Feb 7, 2011 · Last year Nate Silver wrote a piece in the NY Times making exactly your point: "The key difference in Pecota, the forecasting system that I ...Missing: origins | Show results with:origins
[10]
BP Unfiltered: PECOTA, Pitcher WARP, and PADE Updates
Jul 19, 2011 · Rest-of-season PECOTA: We've made changes to the weighting of recent results that reduced the impact of 2009-2010 performance on players' rest- ...Missing: revisions xFIP
[11]
Information-Based Updates to Projections - Baseball Prospectus
Jun 28, 2021 · Pitchers similarly have received updated rest-of-season projections, although theirs tend to be a bit more aggressive, especially on the high ...
[12]
PECOTA 2025: An Introduction | Baseball Prospectus
Feb 3, 2025 · Traditionally, PECOTA projects individual batting events: not only strikeouts and walks, but singles, doubles, triples, home runs, etc. However, ...Missing: explanation | Show results with:explanation
[13]
A guide to the projection systems - Beyond the Box Score
Feb 22, 2016 · PECOTA, like Marcel, begins by calculating a baseline for each player using their past performances, with more recent years weighted more ...
[14]
Statistical Projections and you, Part 1 | Twinkie Town
Feb 28, 2020 · PECOTA, which stands for Player Empirical Comparison and Optimization Test Algorithm, is Baseball Prospectus' proprietary system that projects ...
[15]
Baseball Prospectus News: 10-Year Projections, UPSIDE ...
Mar 12, 2014 · 10-Year Forecast: A projection of player performance over the next decade. UPSIDE: Not all players with the same projection have the same ...
[16]
BP Unfiltered: A few quick words about PECOTA | Baseball Prospectus
Feb 2, 2011 · The comparables represent a lot of tedious number crunching (measuring Euclidean distance in n-th dimensional space, if you want to be precise).Missing: methodology comparable
[17]
View details for PECOTA - Baseball Prospectus | Glossary
PECOTA stands for Player Empirical Comparison and Optimization Test Algorithm. It projects player performance based on historical player-seasons.Missing: explanation | Show results with:explanation
[18]
Fun with PECOTA Comparisons - Royals Review
Jun 8, 2014 · Comparable Players are generated by taking a player's baseline projection and finding players with the same age and similar contact, power ...Missing: methodology | Show results with:methodology
[19]
View details for Percentile Forecast - Baseball Prospectus | Glossary
PECOTA forecasts playing time (plate appearances) in addition to a player's rate statistics. These forecasts are based on a player's previous record of ...
[20]
Manufactured Runs: Out of Sequence | Baseball Prospectus
### Summary of PECOTA's Use of Peripheral Statistics and Adjustments
[21]
An Updated System of Park Factors (and Volatility)
Feb 9, 2021 · We introduce the updated family of BP Park Factors. These park factors offer several features: Our new park factors are reflected in our PECOTA projections for ...Missing: era | Show results with:era
[22]
Glossary: PECOTA - Baseball Prospectus
PECOTA is BP's proprietary system that projects player performance based on comparison with historical player-seasons. There are three elements to PECOTA: 1) ...
[23]
Reintroducing PECOTA: The Seven Percent Solution
Oct 1, 2010 · Why? Fundamentally, players who perform above their expectations are more likely to get playing time than players who perform below their ...
[24]
Introducing PECOTA 2021: Short Seasons, Variance, and ...
Feb 1, 2021 · PECOTA thinks that Kershaw will be exceptionally good, and that Kopech will be slightly above average. In that respect, PECOTA may not differ ...
[25]
Baseball Prospectus Basics: The Science of Forecasting
Mar 11, 2004 · My name is Nate, and I am a forecaster. I forecast how baseball players are going to perform. And I pretty much get the worst of it. Tell ...Missing: origins | Show results with:origins
[26]
View details for Pen Support - Baseball Prospectus | Glossary
Negative Pen Support means the bullpen prevented more runs from scoring than an average pen (i.e. the pitcher's ERA looks better than it should because of good ...
[27]
https://legacy.baseballprospectus.com/glossary/index.php?mode=viewstat&stat=193
[28]
An Updated Evaluation of Hitting and Pitching (Including Stuff ...
May 3, 2023 · Shortly after its introduction, we advised that for pitchers, xwOBA was performing no better than FIP, and not as well as DRA. Likewise upon ...
[29]
A Depth Chart Playing Time Primer | Baseball Prospectus
Feb 1, 2021 · This information is all drawn from the depth charts, which are updated manually to project shares of playing time at every position.
[30]
Spitballing: Playing with Playing Time | Baseball Prospectus
Feb 24, 2011 · For batters, that means that you project with 80 percent of the previous year's plate appearances, and for pitchers it's closer to 75 percent.
[31]
Just how good can Aaron Judge get? - Pinstripe Alley
May 9, 2022 · At the start of the season, PECOTA's 99th-percentile projection for Judge was a seven-win, 1.035 OPS player, with the system dinging him for ...
[32]
Skewed Left: Quoth PECOTA "Nevermore" | Baseball Prospectus
However, that's not how PECOTA works. It treats the team projection as the sum of individuals, all of whom came from different places, are at different ...
[33]
Projected 2025 standings and playoff odds are here - MLB.com
Feb 4, 2025 · The PECOTA projections over at Baseball Prospectus are one of the big ones, and the projected standings and playoff odds for the 2025 season were released this ...
[34]
The AX - Fantasy Baseball Auction Draft Tools
The AX allows you to create customized valuations or rankings based on your personal opinions on players by leveraging PECOTA's percentile projections. It works ...
[35]
Fantasy | Baseball Prospectus
A PECOTA-based tool designed to help you prepare for your fantasy auction or draft, no matter your league or draft format.
[36]
Tools of Ignorance: The Trades Remain the Same
Aug 18, 2016 · The Cespedes trade was fine value for value and had a certain amount of surplus baseball strategy value that is easy to understand for folks who ...Missing: influence | Show results with:influence
[37]
Sabermetrician Silver predicts election and comes up perfect
Nov 7, 2012 · Remember Nate Silver? Back in 2002, he developed PECOTA (Player Empirical Comparison and Optimization Test Algorithm), a sabermetric system ...
[38]
Lies, damn lies, and projections - ESPN
Feb 27, 2019 · Lies, damn lies, and projections. Kyle Schwarber and the Cubs are the latest team to be unhappy about their poor PECOTA projection.
[39]
Lies, Damned Lies: PECOTA Takes On Prospects, Part One
Feb 8, 2006 · Although PECOTA is very good at what it does, it has some limitations: PECOTA is not especially good about accounting for injuries. Although ...
[40]
Why PECOTA projections were so wrong about the Cubs - ESPN
May 21, 2019 · Why PECOTA was so low on the Cubs: Here's what a team projection really is: PECOTA runs individual projections for every player, based mostly on ...
[41]
The Projection Rundown: The Basics on Marcels, ZiPS, CAIRO ...
Feb 16, 2011 · It's a comparatively simple projection system – using weighted averages of the past three seasons of data, and adjusting for aging and ...
[42]
10 Lessons I Have Learned about Creating a Projection System
Apr 30, 2014 · Dan Szymborski is a senior writer for FanGraphs and the developer of the ZiPS projection system. He was a writer for ESPN.com from 2010-2018, a ...Missing: methodology | Show results with:methodology
[43]
Projection Systems | Sabermetrics Library - FanGraphs
Feb 25, 2010 · Some like ZiPS, Steamer, Oliver, etc use much more advanced methodologies to estimate how well they think a player will perform using all sorts ...
[44]
The ATC Volatility Metrics | RotoGraphs Fantasy Baseball - FanGraphs
Feb 5, 2025 · Take the Steamer projection system for example. Steamer uses their proprietary methodology to project future player performance. According ...
[45]
The ATC Projection System - RotoGraphs Fantasy Baseball
Mar 1, 2017 · The Average Total Cost System was developed by Ariel Cohen before the 2011 MLB season for the purposes of winning fantasy baseball leagues. ...
[46]
View details for Comparable Players - Baseball Prospectus | Glossary
Comparable Players are generated by taking a player's baseline projection and finding players with the same age and similar contact, power on contact, walks, ...
[47]
2025 Special Blend Projections for Fantasy Baseball - Mr. Cheatsheet
Mar 14, 2025 · Top Projected Players. Top Hitters by WERTH. 1.Shohei Ohtani (DH)LAD • DH. 14.3. 2.Bobby Witt Jr.KC • SS. 10.1. 3.Aaron JudgeNYY • OF. 10.0. 4.
[48]
Evaluating The 2014 Projection Systems | The Hardball Times
Dec 18, 2014 · Property of Baseball Prospectus and developed by Nate Silver, rather than using weighted averages, PECOTA uses a system of historical player ...Methodology · Results · Experience
[49]
PECOTA Takes on the Field: How'd it Fare Against Six Other ...
Jan 16, 2004 · 2004 PECOTA Weighted Mean Projections are available for Baseball Prospectus Premium subscribers to download. Last year at this time, ...
[50]
FanGraphs Prep: Build and Test Your Own Projection System
May 20, 2020 · The Marcel the Monkey Forecasting System is the most basic projection system used in baseball. It's simply a weighted mean of the past three years of data.
[51]
Retrosheet - BR Bullpen - Baseball-Reference.com
Apr 10, 2023 · Retrosheet was founded by David W. Smith in 1989 for the purpose of computerizing play-by-play accounts of as many pre-1984 major league games as possible.Missing: PECOTA evaluation
[52]
Reintroducing PECOTA: Whatever Happened to the Man of ...
Sep 28, 2010 · (Obviously with some things, like minor league stats, we're not going to be able to do 60 years worth of tests, but the concept is similar.)
[53]
2015's projection systems in review, part one - Beyond the Box Score
Jan 14, 2016 · Marcel and Steamer had the best results, so they added accuracy to each category, while PECOTA and ZiPS reduced it. Marcel, as the most ...Missing: Statcast integration
[54]
2015's projections systems in review, part two - Beyond the Box Score
Jan 21, 2016 · The sample is composed of all pitchers with more than 0 innings pitched (IP) who had a projection from all three of PECOTA, Steamer, and ZiPS.
[55]
(PDF) The Prediction of Batting Averages in Major League Baseball
Apr 3, 2020 · This paper considers the use of ball-by-ball data provided by the Statcast system in an attempt to predict batting averages. The publicly ...
[56]
https://www.baseballprospectus.com/news/article/16189/reintroducing-pecota-house-of-cards/
[57]
Reintroducing PECOTA: House of Cards | Baseball Prospectus
Mar 8, 2012 · Debuting on the cards are the 10-year forecasts and the percentile forecasts. The 10-year projection process breaks down like so: First, a ...