Glossary: PECOTA

See Percentile Forecast.

Attrition Rate is the percent chance that a hitter's plate appearances or a pitcher's opposing batters faced will decrease by at least 50% relative to his Baseline playing time forecast. Although it is generally a good indicator of the risk of injury, Attrition Rate will also capture seasons in which his playing time decreases due to poor performance or managerial decisions.

Batting Average on balls put into play. A pitcher's average on batted balls ending a plate appearance, excluding home runs. Based on the research of Voros McCracken and others, BABIP is mostly a function of a pitcher's defense and luck, rather than persistent skill. Thus, pitchers with abnormally high or low BABIPs are good bets to see their performances regress to the mean. A typical BABIP is about .290.

The Baseline forecast, although it does not appear here, is a crucial intermediate step in creating a player's forecast. The Baseline developed based on the player's previous three seasons of performance. Both major league and (translated) minor league performances are considered.

The Baseline forecast is also significant in that it attempts to remove luck from a forecast line. For example, a player who hit .310, but with a poor batting eye and unimpressive speed indicators, is probably not really a .310 hitter. It's more likely that he's a .290 hitter who had a few balls bounce his way, and the Baseline attempts to correct for this.

Batting average; hits divided by at-bats. In PECOTA, Batting Average is one of five primary production metrics used in identifying a hitter's comparables. It is defined as H/AB.

A measure of the relative volatility of a player's EqA or EqERA forecast, as determined from his comparables. The Beta for an average major league player is 1.00; players with Beta's higher than 1.00 have more volatile forecasts than others ("riskier"), while Betas lower than 1.00 represent less volatile forecasts ("less risky"). Betas are adjusted for the amount of playing time that a player is expected to receive. Thus, a player's Beta will not be higher simply because he's expected to receive less playing time (as a relief pitcher might as compared with a starter, for example), which naturally produces more variance because of higher sample sizes. Betas may be unreliable for players with few appropriate comparables.

Breakout Rate is the percent chance that a hitter's EqR/27 or a pitcher's EqERA will improve by at least 20% relative to the weighted average of his EqR/27 in his three previous seasons of performance. High breakout rates are indicative of upside risk.

Breakout rates measure change relative to a player's previously-established level of performance. For this reason, a high Breakout score can create a falsely optimistic picture for a player who has a very poor performance record. It is far easier for a player with a baseline of 40 EqR per season to improve upon that figure by 20% than it is for a player with a baseline of 100 EQR per season; as a result, his Breakout score is likely to be higher (see also Ugueto Effect).

Career Path Analysis is the name for a chart on a player's PECOTA card. The solid, curved lines represent a player's VORP at his 90th, 75th, 60th, 50th (Median), 40th, 25th and 10th percentile levels of performance over the course of his next five seasons. All of these lines appear in BLUE, except for a player's Median/50th percentile forecast, which appears in RED.

For hitters, Collapse Rate is the percent chance that the player's EqR/27 will decrease by at least 20% relative to the weighted average of his EqR/27 in his three previous seasons of performance. For pitchers, Collapse Rate is the percent chance that a pitcher's EqERA will increase by at least 25% relative to his baseline EqERA over his past three seasons. High Collapse Rates are indicative of downside risk.

Comparable Players are the backbone of a player's PECOTA. Only the twenty best comparables are listed here, but as many as 100 players may be used in the generation of his forecast if they are sufficiently comparable.

PECOTA compares each player against a database of roughly 20,000 major league batter seasons since World War II. In addition, it also draws upon a database of roughly 15,000 translated minor league seasons (1997-2006) for players that spent most of their previous season in the minor leagues. (When minor league comparables are used, they appear in ALL CAPS). PECOTA considers four broad categories of attributes in determining a hitter's comparability:

1. Production metrics--such as batting average, isolated power, and unintentional walk rate for hitters, or strikeout rate and groundball rate for pitchers.

2. Usage metrics, including career length and plate appearances or innings pitched.

3. Phenotypic attributes, including handedness, height, weight, career length (for major leaguers), and minor league level (for prospects).

4. Fielding Position (for hitters) or starting/relief role (for pitchers). PECOTA doesn't require that a comparable hitter play the same defensive position; it is a factor that is evaluated along with many others, and assigned a relatively substantial weight. Consideration is also given to the 'similarity' between two positions; for example, a shortstop will be compared to a second baseman before he is compared to a left fielder. In most cases, the database is large enough to provide a meaningfully large set of appropriate comparables. When it isn't, the program is designed to 'cheat' by expanding its tolerance for dissimilar players until a reasonable sample size is reached.

Comparable Year represents the season analogous to the current projected year for a comparable player. For example, if Dick Allen is listed as a comparable, and the year listed next to his name is 1974, Allen's 1974 is used as a component of the player's forecast. It also indicates that Allen's Baseline performance entering into the 1974 season was similar to the Baseline performance of the player in question.

PECOTA constructs a 182-day interval on either side of a player's birthdate in order to match ages; this method is more precise than the Bill James similarity scores, which use a player's age as of July 1.

A player's defensive wins above replacement, as listed on his PECOTA card, and accounting for the value of his position and the quality of his defense. Analagous to FRAR.

Defense, as listed in a player's PECOTA card, provides the player's number of defensive games played, primary position, and fielding runs above average (FRAA) with a given team in a given season.

Diagnostics are a series of metrics designed to estimate the probability of certain types of changes in production and playing time; see the individual entries for additional detail.

Drop Rate is the percent chance that a player will not receive any major league plate appearances in a given season, based on comparables who disappear from the dataset entirely. Because of the conventions PECOTA uses in selecting comparables, the Drop Rate is always assumed to be zero for the current year, but it is an important consideration in a hitter's Five-Year Forecast.

Also known as a BSP chart, an acronym for bloodstain spatter pattern, which these graphs seem to bear an eerie resemblance toward. The BSP charts plot a rate performance statistic (EqA or EqERA) on the one axis and playing time on the other (PA or IP). Each of the diamonds you see represents the performance implied by one of a player’s comparables; the higher the similarity score for that comparable, the larger the size of the diamond. There is also an area of the chart shaded in a yellow color; this is the ‘golden zone’ of performance in which a player both performs well (an EqA of .300 or higher) and remains in the lineup frequently (at least 500 plate appearances). Pitchers actually have two golden zones, one each for roles as starting pitchers and relievers.

In PECOTA projections, the ERA Distribution chart displays a pitcher's ERA forecast at various levels of probability. It progresses in sequential intervals of five percentage points, ranging from a pitcher's 95th percentile forecast on the left, to his 5th percentile forecast on the right.

In addition to the probability distribution for a given pitcher, which appears in blue, the chart also includes a normal distribution on ERA for all pitchers in the league, as adjusted to the player's current park and league context ("Norm"), and a dashed line representing the performance of a replacement level pitcher ("Replace").

Equivalent Batting Average, sometimes also referred to as Translated or Normalized Batting Average. This is a player's batting average, adjusted for ballpark, league difficulty, and era, and calibrated to an ideal major league where the overall EqBA is .260. While a major league hitter's equivalent stats should not differ substantially from his actual numbers, a minor league hitter's equivalent stats undergo translation and may differ significantly.

EqBA, or Equivalent Batting Average, is calibrated to an ideal major league with an overall EqBA of .270. While a major league hitter's equivalent stats should not differ substantially from his actual numbers, a minor league hitter's equivalent stats undergo translation and may differ significantly. Equivalent stats also account for park effects.

EqBB9 is calibrated to an ideal major league where EqBB9 = 3.0. While a major league pitcher's equivalent stats should not differ substantially from his actual numbers, a minor league pitcher's equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects.

EqERA is calibrated to an ideal major league where EqERA = 4.50. While a major league pitcher's equivalent stats should not differ substantially from his actual numbers, a minor league pitcher's equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects, and the quality of a pitcher's defense. EqERA is conceptually identical to NRA, as used in the DT cards.

EqH9 is calibrated to an ideal major league where EqH9 = 9.0. While a major league pitcher's equivalent stats should not differ substantially from his actual numbers, a minor league pitcher's equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects.

EqHR9 is calibrated to an ideal major league where EqHR9 = 1.0. While a major league pitcher's equivalent stats should not differ substantially from his actual numbers, a minor league pitcher's equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects.

EqK9 is calibrated to an ideal major league where EqK9 = 6.0. While a major league pitcher's equivalent stats should not differ substantially from his actual numbers, a minor league pitcher's equivalent stats undergo translation and may differ significantly. Equivalent stats also adjust for park effects.

EqMLVr, or Equivalent rate-based Marginal Lineup Value, is calibrated to an ideal major league with an overall EqMLVr of .000. While a major league hitter's equivalent stats should not differ substantially from his actual numbers, a minor league hitter's equivalent stats undergo translation and may differ significantly. Equivalent stats also account for park effects.

EqOBP, or Equivalent On Base Percentage, is calibrated to an ideal major league with an overall EqOBP of .340. While a major league hitter's equivalent stats should not differ substantially from his actual numbers, a minor league hitter's equivalent stats undergo translation and may differ significantly. Equivalent stats also account for park effects.

EqSLG, or Equivalent Slugging Percentage, is calibrated to an ideal major league with an overall EqSLG of .440. While a major league hitter's equivalent stats should not differ substantially from his actual numbers, a minor league hitter's equivalent stats undergo translation and may differ significantly. Equivalent stats also account for park effects.

The Five-Year Attrition forecast measures a player's Attrition Rate and Drop Rate over the forthcoming five seasons. These forecasts consider only players who have completed the comparable year in question.

The Five-Year Forecast is a player's weighted mean PECOTA forecast, taken over his next five seasons.

The Five-Year Performance forecast measures a hitter's forecast EqA or a pitcher's EqERA at various percentiles (90th, 75th, 60th, 50th, 40th, 25th and 10th) over the course of the next five seasons. The percentile forecasts are indicated by solid lines, usually in BLUE, except for his median/50th percentile forecast which is indicated in RED. Also listed is the player's weighted mean forecast in that category, indicated with a dashed YELLOW line.

The Five-Year WARP forecast measures a player's projected wins above replacement. For position players, this value is subdivided into batting wins, and defensive wins.

Groundball Percentage. The number of groundballs that a pitcher allows as a percentage of all balls hit into play. Our definition of GB% does not count line drives or popups as groundballs, and considers all batted balls put into play, not just those that result in outs. Because of this defintion, the league average GB% is somewhat lower than than what may be listed in other venues, or about 44%.

See BABIP.

Historical Stats are the player's previous three seasons of performance as they appear in the BP book (with the addition of a player's WARP scores).

Isolated Power (ISO) is a measure of a hitter's raw power, in terms of extra bases per AB. Its formula is ISO = (2B + (3B*2) + (HR*3)) / AB

In PECOTA, ISO is one of five primary production metrics used in identifying a hitter or pitcher's comparables. PECOTA uses a slightly modified version of Isolated Power that assigns the same value to triples as to doubles (extending a double into a triple is generally an indicator of speed, rather than additional power). Thus, the formula for PECOTA isolated power as follows: ISO = (2B + 3B + (HR*3)) / AB

Improvement Rate is the percent chance that a hitter's EqR/27 or a pitcher's EqERA will improve *at all* relative the weighted average of his EqR/27 or EqERA in his three previous seasons of performance. A player who is expected to perform just the same as he has in the past will have an Improvement Rating of 50%.

The Jeremy Giambi Effect is a name given to the correlation between playing time and quality of performance. The Jeremy Giambi Effect has important implications for understanding a player's PECOTA forecast.

League. 'A' or 'AL' denotes American League. 'N' or 'NL' denotes National League.

Marginal Lineup Value, a measure of offensive production created by David Tate and further developed by Keith Woolner. MLV is an estimate of the additional number of runs a given player will contribute to a lineup that otherwise consists of average offensive performers. Additional information on MLV can be found here.

MLVr is a rate-based version of Marginal Lineup Value (MLV), a measure of offensive production created by David Tate and further developed by Keith Woolner. MLV is an estimate of the additional number of runs a given player will contribute to a lineup that otherwise consists of average offensive performers. MLVr is approximately equal to MLV per game. The league average MLVr is zero (0.000). Additional information on MLV and MLVr can be found here.

Marginal Value Above Replacement Player, as introduced in this article. MORP is modelled based on the actual behavior of recent free agent markets, and accounts for non-linearity in the market price of baseball talent (e.g. teams are willing to pay more for one 6-win player than two 3-win players).

A player's offensive wins above replacement, as listed on his PECOTA card. Analagous to BRAR.

'Out of Baseball' is the tag assigned to a player's five-year forecast when his Drop Rate in that season exceeds 66.7%. That is, we do not list a player's forecast line when it is substantially more likely than not that he will not be playing professional baseball.

PEAK refers to a series of metrics designed to evaluate a player's value over a consecutive six year period, as forecast by PECOTA.

Stands for Player Empirical Comparison and Optimization Test Algorithm. PECOTA is BP's proprietary system that projects player performance based on comparison with thousands of historical player-seasons. PECOTA analyzes similarities with past player-seasons based not only on rate statistics, but also height, weight, age, and many other factors.

PERA is a pitcher's ERA as estimated from his peripheral statistics (EqH9, EqHR9, EqBB9, EqK9). Because it is not sensitive to the timing of batting events, PERA is less subject to luck than ERA, and is a better predictor of ERA going-forward than ERA itself. Like the rest of a pitcher's equivalent stats, his PERA is calibrated to an ideal league with an average PERA of 4.50.

The Percentile Forecast is a representation of the player's expected performance in the upcoming season at various levels of probability. For example, if a pitcher's 75th percentile EqERA forecast is 3.50, this indicates that he has a 75% chance to post an EqERA of 3.50 or higher, and a 25% chance to post an EqERA lower than 3.50. Higher percentiles indicate more favorable outcomes.

A player's forecast is adjusted to the park and league context associated with the team listed at the top of the forecast page. Team dependant stats like Wins, RBIs, and BABIP account for the projected performance level of a player's teammates

For Hitters:

The Player Profile is a chart that evaluates a given hitter's primary production metrics (batting average, isolated power, unintentional walk rate, strikeout rate, and speed score) as a percentile compared to all major league hitters. For example, a player with an isolated power rating of 75% is superior in this category to three-quarters of all major leaguers. The player profile is based on the player's three previous seasons of performance, rather than his projection.

For Pitchers:

The Player Profile is a chart that evaluates a pitcher's performance in five categories: strikeout rate, walk rate, opponents' isolated power (e.g. home run rate), hit rate on balls in play, and groundball-to-flyball ratio. The rates are presented as a percentile compared to all major league pitchers; for example, a player with a strikeout rating of 75% is superior in this category to three-quarters of all major leaguers. The player profile is based on the player's three previous seasons of performance, rather than his projection.

For PECOTA, a player's Position is a consideration in identifying his comparables, as well as in calculating his VORP. The player's primary position as used by PECOTA is listed at the top of his forecast page; however, secondary and tertiary positions are also considered based on the relative amount of appearances that a player receives there. The position determination is made primarily based on the position(s) that a player appeared in his most recent season, with lesser consideration given to the position(s) he appeared other recent previous seasons. Both major league and minor league defensive appearances are considered in the determination of a player's position, but major league appearances are weighted more heavily. PECOTA considers LF, CF and RF to be separate positions.

When listed numerically on our statistical reports, positions are: 1, pitcher; 2, catcher; 3, first base; 4, second base; 5, third base; 6, shortstop; 7, left field; 8, center field; 9, right field; 10, designated hitter; 11, pinch hitter; 12, pinch runner.

QERA, or QuikERA, was described most verbosely by Nate Silver in this article:

QuikERA (QERA), which estimates what a pitcher's ERA should be based solely on his strikeout rate, walk rate, and GB/FB ratio. These three components--K rate, BB rate, GB/FB--stabilize very quickly, and they have the strongest predictive relationship with a pitcher’s ERA going forward. What’s more, they are not very dependent on park effects, allowing us to make reasonable comparisons of pitchers across different teams.

The formula for QERA is as follows:

QERA =(2.69+K%*(-3.4)+BB%*3.88+GB%*(-0.66))^2

Note that everything ends up expressed in terms of percentages: strikeouts per opponent plate appearance, walks per opponent plate appearance, and groundballs as a percentage of all balls hit into play. Andy Pettitte, for example, has a 19.6% K rate, a 7.9% BB rate, and a 62.7% GB rate, giving him a QERA of 3.68. Note further that QERA is exponential, which is appropriate since run scoring is not linear.

Abbreviation for Speed Score as used in PECOTA cards.

(or SS/Sim) Runs above Replacement for Scoresheet Baseball (SS). This should also be helpful for other sim leagues. This statistic accounts for:

Similarity Index is a composite of the similarity scores of all of a player's comparables. Similarity index is a gauge of the player's historical uniqueness; a player with a score of 50 or higher has a very common typology, while a player with a score of 20 or lower is historically unusual. For players with a very low similarity index, PECOTA expands its tolerance for dissimilar comparables until a meaningful sample size is established (see Comparable Players).

Similarity Score is a relative measure of a player's comparability. Its scale is very different from the Bill James similarity scores; a score of 100 is assigned to a perfect comparable, while a score of 0 represents a player who is meaningfully similar. Players can and frequently do receive negative similarity scores, and they are dropped from the analysis. A score above 50 indicates that a player is substantially comparable, and scores in excess of 70 are very unusual. The comparable player observations are weighted based on their similarity score in constructing a forecast.

Speed Score (SPD) is one of five primary production metrics used by PECOTA in identifying a hitter's comparables. It is based in principle on the Bill James speed score and includes five components: Stolen base percentage, stolen base attempts as a percentage of opportunities, triples, double plays grounded into as a percentage of opportunities, and runs scored as a percentage of times on base.

The Stars & Scrubs Chart represents the probability that a player will demonstrate a given level of performance over the course of his next five seasons.

In PECOTA, stolen base attempts as a percentage of times on first base.

Strikeout Rate (K) is one of five primary production metrics used by PECOTA in identifying a player's comparables. It is defined as SO/PA.

A rough indicator of the pitcher's overall dominance, based on normalized strikeout rates, walk rates, home run rates, runs allowed, and innings per game. "10" is league average, while "0" is roughly replacement level. The formula is as follows: Stuff = EqK9 * 6 - 1.333 * (EqERA + PERA) - 3 * EqBB9 - 5 * EqHR9 -3 * MAX{6-IP/G),0}

As listed on a player's PECOTA card, SuperVORP is VORP with additional adjustments for the following: 1) League difficulty. Players in a more difficult league (e.g. the American League) receive a boost in their SuperVORP to reflect their work against tougher competition. 2) Defensive support (for pitchers). A pitcher's BABIP, and therefore his VORP, are affected by his defense. SuperVORP adjusts the pitcher's VORP by assuming he has a league average defense behind him. 3) Fielding runs above average (FRAA) (for position players). The number of runs a player saves or subtracts with his glove, relative to league average, is added to his SuperVORP score. SuperVORP can be thought of as analogous to WARP, but with a higher threshold for replacement level.

As used in most places (including the PECOTA cards), Team is the three letter abbreviation for a major league, minor league, or foreign team. This page contains the list of teams and their abbreviations.

The Davenport Translations Player Cards have slightly different abbreviations, with a three-character team signifier, followed by a league signifier. The leagues are as follows: N signifies the National Association of 1871-1875 and the National League of 1876-present. A is for both the American Association (1882-1891, a major league, separate from the later minor league of the same name) and the 1901-present American League. U is the Union Association of 1884, P the Players League of 1890, and F the Federal League of 1914-15. For example, the Boston Red Sox are BOS-A, where the "A" signifies an American League team, while BOS-N refers to the Boston Braves National League franchise. At this time, for players who played for more than one team in a season, the order in which the various team stints are shown is not necessarily chronological.

Total WARP (Wins Above Replacement) as listed on his PECOTA card, considering both a player's offensive and defensive contributions. See WARP1.

Trend identifies players who demonstrate dramatic changes from their Baseline during their comparable year.

For Hitters:

Hitters who improve their EqR/PA by at least 20% are identified by a green, upward-pointing arrow and contribute to a hitter's Breakout score; hitters whose EqR/PA decreases by at least 20% are identified by a red, downward-pointing arrow and contribute to a hitter's Collapse score.

For Pitchers:

Pitchers who improve their EqERA by at least 20% are identified by a green, upward-pointing arrow and contribute to a pitcher's Breakout score; pitchers whose EqERA increases by at least 25% are identified by a red, downward-pointing arrow and contribute to a pitcher's Collapse score.

UPSIDE is determined by evaluating the performance of a player's PECOTA comparables. If a comparable player turned in a performance better than league average, including both his batting and fielding performance, then twice the number of runs he contributed above average is counted toward his UPSIDE. If the player was worse than league average, or he dropped out of the database, the performance is counted as zero.

The Ugueto Effect is name given to the phenomenon in which very poor players are associated with very high PECOTA Breakout scores. It is far easier for a player like Luis Ugueto, who would produce about 40 EQR over a full season, to improve upon that figure by 20% than it is for Alex Rodriguez; as a result, his Breakout score is likely to be higher. This does not mean that Ugueto is a player you'd want anywhere near your roster.

Unintentional Walk Rate (BB) is one of five primary production metrics used by PECOTA in identifying a player's comparables. It is defined as (BB-IBB)/PA.

Value Over Replacement Player. The number of runs contributed beyond what a replacement-level player at the same position would contribute if given the same percentage of team plate appearances. VORP scores do not consider the quality of a player's defense.

See also RARP.

As listed in a player's PECOTA card, a series of metrics designed to evaluate a player's value to his team going forward. See individual entries for detail.

Wins Above Replacement Player, level 1. The number of wins this player contributed, above what a replacement level hitter, fielder, and pitcher would have done, with adjustments only for within the season. It should be noted that a team which is at replacement level in all three of batting, pitching, and fielding will be an extraordinarily bad team, on the order of 20-25 wins in a 162-game season.

Walks plus hits allowed per inning pitched.

Expected wins added over a replacement level pitcher, adjusted for level of opposing hitters. WXRL combines the individual adjustments for replacement level (WXR) and quality of the opposing lineup (WXL) to the basic WX calculation.

The Weighted Mean forecast incorporates all of the player's potential outcomes into a single average, weighted baed on projected playing time. In almost all cases, poor performances are associated with a reduced number of plate appearances. For that reason, they don't hurt a player's team quite as much as good performances help it; the weighting is designed to compensate for this effect (see also Jeremy Giambi Effect).

See WARP-1.