Baseball Prospectus Glossary

Errors.

Expected loss record for the pitcher, based on how often pitchers with the same innings pitched and runs allowed earned a win or loss historically (this differs from how it was computed, which was a more complicated, theoretical calculation).

Expected win record for the pitcher, based on how often pitchers with the same innings pitched and runs allowed earned a win or loss historically (this differs from how it was computed, which was a more complicated, theoretical calculation).

Expected winning percentage for the pitcher, based on how often a pitcher with the same innings pitched and runs allowed in each individual game earned a win or loss historically in the modern era (1972-present).

Rate version of END_GAME: percentage of the player's plate appearances that were the last PA of the game.

Number of times the player had the last plate appearance of the game.

EPAA - Errant Pitches Above Average - is the official name for Passed Balls and Wild Pitches above average. Please click here for details: Errant Pitches Above Average

Unfortunately, Passed Balls or Wild Pitches Above Average would be quite a mouthful. Again, we're trying out a new term to see if it is easier to communicate these concepts. We're going to call these events Errant Pitches. The statistic that compares pitchers and catchers in these events is called Errant Pitches Above Average, or EPAA.

(from http://bbp.cx/a/26195)

Under baseball’s scoring rules, a wild pitch is assigned when a pitcher throws a pitch that is deemed too difficult for a catcher to control with ordinary effort, thereby allowing a baserunner (including a batter, on a third strike) to advance a base. A passed ball is assigned when a pitcher throws a pitch that a catcher ought to have controlled with ordinary effort, but which nonetheless gets away, also allowing a baserunner to move up a base. The difference between a wild pitch and a passed ball, like that of the “earned” run, is at the discretion of the official scorer. Because there can be inconsistency in applying these categories, we prefer to consider them together.

Last year, Dan Brooks and Harry Pavlidis introduced a regressed probabilistic model that combined Harry’s pitch classifications from PitchInfo with a With or Without You (WOWY) approach. RPM-WOWY measured pitchers and catchers on the number and quality of passed balls or wild pitches (PBWP) experienced while they were involved in the game.

Not surprisingly, we have updated this approach to a mixed model as well. Unfortunately, Passed Balls or Wild Pitches Above Average would be quite a mouthful. Again, we’re trying out a new term to see if it is easier to communicate these concepts. We’re going to call these events Errant Pitches. The statistic that compares pitchers and catchers in these events is called Errant Pitches Above Average, or EPAA.

Unfortunately, the mixed model only works for us from 2008 forward, which is when PITCHf/x data became available. Before that time, we will rely solely on WOWY to measure PBWP, which is when pitch counts were first tracked officially. For the time being, we won’t calculate EPAA before 1988 at all, and it will not play a role in calculating pitcher DRA for those seasons.

But, from 2008 through 2014, and going forward, here are the factors that EPAA considers:

• The identity of the pitcher;
• The identity of the catcher;
• The likelihood of the pitch being an Errant Pitch, based on location and type of pitch, courtesy of PitchInfo classifications.

Errant Pitches, as you can see, has a much smaller list of relevant factors than our other statistics.

In 2014, the pitchers with the best (most negative) EPAA scores were:

And the pitchers our model said were most likely to generate a troublesome pitch were:

Runs a catcher saves (usually over the course of a season), based on EPAA.

There's a factor for each year-level combination which varies from less than 0.20 to more than 0.33, averaging around 0.27. This factor is multiplied times EPAA times EPAA chances (Blocking Chances) to get EPAA Runs (or Blocking Runs).

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.

Earned Runs.

Earned Run Average. Earned runs, divided by innings pitched, multiplied by nine.

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").

Expected Return Date: An estimate of the date a player is expected to return to the lineup/rotation based on the current information. A player listed as "10/4" is done for the season; October 4th is the final day of the regular season.

Expected runs scored with zero outs

Expected runs scored with one out

Expected runs scored with two outs

Run differential (team at bat - team in field)

the difference between actual and predicted strikes received by the catcher

the difference between actual and predicted strikes received by the catcher

Equivalent Average. A measure of total offensive value per out, with corrections for league offensive level, home park, and team pitching. EQA considers batting as well as baserunning, but not the value of a position player's defense. The EqA adjusted for all-time also has a correction for league difficulty. The scale is deliberately set to approximate that of batting average. League average EqA is always equal to .260.

EqA is derived from Raw EqA, which is

RawEqA =(H+TB+1.5*(BB+HBP+SB)+SH+SF-IBB/2)/(AB+BB+HBP+SH+SF+CS+SB)

Any variables which are either missing or which you don't want to use can simply be ignored (be sure you ignore it for both the individual and league, though). You'll also need to calculate the RawEqa for the entire league (LgEqA).

Convert RawEqA into EqR, taking into account the league EqA LgEqA, league runs per plate appearance, the park factor PF, an adjustment pitadj for not having to face your own team's pitchers, and the difficulty rating. Again, you can ignore some of these as the situation requires. xmul can simply be called "2", while the PF, diffic, and pitadj can be set to "1".

xmul=2*(.125/PF/Lg(R/PA)/pitadj)

EQAADJ=xmul*(RawEqa/LgEqa)* ((1+1/diffic)/2) + (1-xmul)

UEQR=EQAADJ*PA*Lg(R/PA)

To get the final, fully adjusted EqA, we need to place this into a team environment.

This is an average team:

AVGTM=Lg(R/Out)*Lg(Outs/game)*PF*Games*(DH adjustment)

The DH adjustment is for playing in a league with a DH. "Games" is the number of games played by this player.

Replacing one player on the average team with our test subject:

TMPLUS=AVGTM+UEQR-OUT*Lg(R/Out)*DH*PF

Get pythagorean exponent

pyexp=((TMPLUS+AVGTM)/Games)**.285

Calculate win percentage

WINPCT=((TMPLUS/AVGTM)**pyexp)/(1+(TMPLUS/AVGTM)**pyexp)

Convert into adjusted space, where the Pythagorean exponent is set to 2.

NEWTM=(WINPCT/(1-WINPCT))**(1/2)

Fully adjusted EqR:

EQR=.17235*((NEWTM-1)*27.*Games + Outs)

Fully adjusted EqA

EQA= (EQR/5/Outs)** 0.4

Equivalent Average, as taken from the Davenport Translation (DT) Player Cards. EqA1 is EqA adjusted for the season in which the performance occurred, as opposed to EqA2, which is adjusted for comparisons across multiple seasons or eras. For example, if you wanted to compare Albert Pujols's 2008 performance against those of other players in the 2008 season, you would reference his EqA1; if you wanted to compare Pujols's 2008 against Lou Gehrig's seasons in the 1920s and 30s, you would reference Pujols's and Gehrig's respective EqA2s.

Air Advancement Runs. The number of theoretical runs contributed by a baserunner or baserunners above what would be expected given the number and quality of their baserunning opportunities. AAR is based on a multi-year Run Expectancy matrix, is park adjusted, and considers the following scenarios:

• Runner on first with second and third unoccupied, less than two outs, a line drive, pop-up, or fly ball is caught by an outfielder
• Runner on second but not third, less than two outs, a line drive, pop-up, or fly ball is caught by an outfielder
• Runner on third with other bases optionally occupied, less than two outs, a line drive, pop-up, or fly ball is caught by an outfielder

Here is an example of the Air Advancement Runs spectrum based on the 2011 season:

Excellent - Alex Gordon 2.68
Great - Robinson Cano 1.21
Average - Brian Bogusevic 0.00
Poor - Yorvit Torrealba -1.43
Horrendous - Adrian Gonzalez -2.28

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.

Ground Advancement Runs. The number of theoretical runs contributed by a baserunner or baserunners above what would be expected given the number and quality of baserunning opportunities. GAR is based on a multi-year Run Expectancy matrix and considers the following scenarios:

• Runner on first only with less than two outs, ground ball or bunt is hit to an infielder where a hit or an error is not credited
• Runner on second only with less than two outs, ground ball or bunt is hit to an infielder where a hit or an error is not credited
• Runner on third only with less than two outs, ground ball or bunt is hit to an infielder where a hit or an error is not credited

Here is an example of the Ground Advancement Runs spectrum based on the 2011 season:

Excellent - Emilio Bonifacio 6.45
Great - Dexter Fowler 2.98
Average - Roger Bernadina 0.01
Poor - Adrian Gonzalez -1.76
Horrendous - Ryan Howard -3.76

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.

Hit Advancement Runs. The number of theoretical runs contributed by a baserunner or baserunners above what would have been expected given the number and quality of opportunities. HAR considers advancement from first on singles, second on singles, and first on doubles and is adjusted for park and based on a multi-year Run Expectancy Matrix.

Here is an example of the Hit Advancement Runs spectrum based on the 2011 season:

Excellent - Dexter Fowler 4.74
Great - Ryan Braun 2.69
Average - James Loney 0.00
Poor - Brett Wallace -2.54
Horrendous - Ryan Howard -5.66

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.

Other Advancement Runs. Measures the number of runs contributed by a player's advancement on the bases, above what would be expected based on the number and quality of the baserunning opportunities with which the player is presented. Other Advancement takes into consideration a player's opportunities and advancement on the basepaths due to wild pitches and passed balls. The run value of this advancement is based on a multi-year run expectancy matrix and park-adjusted.

Here is an example of the Other Advancement Runs spectrum based on the 2011 season:

Excellent - Bobby Abreu 0.92
Great - Angel Pagan 0.40
Average - Drew Stubbs 0.05
Poor - Juan Uribe -0.28
Horrendous - Michael Cuddyer -0.72

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.

True Runs tells of a player's total offensive contribution in runs.

The formula:
Batting Runs Above Average + Plate Appearances * Average Runs Per Plate Appearance

Equivalent Runs allowed by a team.

Equivalent Stolen Base Runs. The number of theoretical runs contributed by a baserunner or baserunners above what would be expected given the number and quality of their baserunning opportunities. EqSBR is based on a multi-year Run Expectancy matrix and considers both stolen base attempts and pick-offs.

Here is an example of the Stolen Base Runs spectrum based on the 2011 season:

Excellent - Tony Campana 2.82
Great - Dustin Pedroia 1.32
Average - Brandon Phillips -0.01
Poor - Jason Bartlett -1.06
Horrendous - Jon Jay -1.91

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 expected win percentage used to run the Monte Carlo sim based on projected strength of team, but exclusive of schedule. Not to be confused with actual expected winning percentage.

For the preseason Playoff Odds Report, this is based on the Depth Chart wins and losses. As the season progresses, a team's observed performance will be incorporated into the expectation as well.