Baseball Prospectus Glossary
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Stolen bases. Not recorded for any league between 1876 and 1885. On the catcher's fielding charts, not available prior to 1978.
Percentage of stolen base attempts that are successful.
Net Stolen Bases, or SB - CS.
Stolen base opportunities: SB + CS + Pickoffs.
The number of team stolen bases accumulated by runners on first base.
The number of team stolen bases accumulated by runners on second base.
The number of team stolen bases accumulated by runners on third base.
Sacrifice flies. The statistical category of "sacrifice flies" did not exist prior to 1954; the concept had been around, on and off, since 1908, but had been always been part of the "SH" category. See SH.
Simple Fielding Runs -- The runs above average contributed by a defender. SFR is a defensive metric currently in a "beta" form based on Retrosheet-style play by play data. SFR for infielders is calculated differently than that for outfielders and for outfielders the metric is park-adjusted.
Sacrifice hits. Not recorded prior to 1894. From 1894-1907, they were essentially the same as the modern rule - a bunt which advanced a baserunner. From 1908-25, they included what we would now call a sacrifice fly (sacrifices increase 25% between 1907 and 1908 as a result). From 1926-30, they included any fly ball on which a runner advanced, not just ones where the runner scored (another 25% increase in 1926). From 1931-38, sacrifice flies were eliminated completely (causing a 45% drop in sacrifices, and a 4-point decline in batting averages); that brought us back to the modern definition of sacrifice hit. In 1939 they re-introduced the run-scoring sac fly (returning to the 1908-25 rules), but eliminated it again in 1940. When sacrifice flies appeared again in 1954, they had their own category, so the rule for what we would call a sacrifice hit has not changed since 1940.
Shutouts.
Sacrifice Hit Rate -- Sacrifices per plate appearance
Skill-Interactive Earned Run Average estimates ERA through walk rate, strikeout rate and ground ball rate, eliminating the effects of park, defense and luck. It adds little value and has been retired from the Baseball Prospectus statistical offerings as of 2011. See Lost in the SIERA Madre for more explanation.
SIERA accounts for how run prevention improves as ground ball rate increases and declines as more whiffs are accrued, while grounders are of more materiality for those who allow a surplus of runners. The formula for SIERA is:
SIERA = 6.145 - 16.986*(SO/PA) + 11.434*(BB/PA) - 1.858*((GB-FB-PU)/PA) + 7.653*((SO/PA)^2) +/- 6.664*(((GB-FB-PU)/PA)^2) + 10.130*(SO/PA)*((GB-FB-PU)/PA) - 5.195*(BB/PA)*((GB-FB-PU)/PA)
where the +/- term is a negative sign when (GB-FB-PU)/PA is positive and vice versa.
This was explained in more detail in the following series: part one, part two, part three, part four, and part five.
It adds little value and has been retired from the Baseball Prospectus statistical offerings as of 2011. See Lost in the SIERA Madre for more explanation.
Situations where a Double Play was possible -- a plate appearance with a runner on first base and less than two outs
Slugging percentage (hitters) or slugging percentage allowed (pitchers). Total bases divided by at-bats.
The Slugging Percentage of Balls Put in Play.
Similar to Batting Average on Balls in Play, SLGBIP gives an impression of the damage done by the balls in play. As seen here.
Support-Neutral Losses. the pitcher's expected number of losses assuming he had league-average support.
Support-Neutral Lineup-adjusted Value Added - like SNVA, but also adjusted for the MLVr of each batter the pitcher faced.
Support-Neutral Lineup-adjusted Value Added (SNVA adjusted for the MLVr of batters faced) per game pitched.
like SNLVA, but comparing to replacement level, rather than average. Replacement level is now being computed the same way in SNVA and in VORP (using the formulas from Keith Woolner's BP 2002 article).
Rate of Support-Neutral Lineup-adjusted Value Added above replacement level
Rate of Support-Neutral Lineup-adjusted Value Added
SNW / (SNW+SNL)
Support-Neutral Value Added - wins above average added by the pitcher's performance.
Support-Neutral Value Added (wins above average added by the pitcher's performance) per game pitched.
like SNVA, but comparing to replacement level, rather than average. Replacement level is now being computed the same way in SNVA and in VORP (using the formulas from Keith Woolner's BP 2002 article).
Rate of Support-Neutral Value Added
Support-Neutral Wins. the pitcher's expected number of wins assuming he had league-average support.
Support-Neutral Wins Above Replacement-level. the number of SNWs a pitcher has above what a .425 pitcher would get in the same number of (Support-Neutral) decisions.
Support-Neutral Winning Percentage
A pitcher's calculated winning percentage given his pitching performances, assuming he had a league average offense and bullpen behind him.
Michael Wolverton gives an explanation of support-neutral stats here.
Formula:
Read about the underlying mathematical method in this article.
Strikeouts. For pitchers, batters struck out, for batters, times struck out.
Percentage of plate appearances that result in a strikeout.
Strikeout to walk ratio: strikeouts divided by walks.
Strikeouts per 9 innings pitched.
Strikeouts per inning pitched
Strikeout Rate -- Strikeouts per plate appearance
Abbreviation for Speed Score as used in PECOTA cards.
SRAA - Swipe Rate Above Average - is the official name for Bases Stolen Above Average. Please click here for details: Swipe Rate Above Average
Type the definition of the term here, or leave the text as it is if you don't want to add a new term.
Swipe Rate, as its name implies, judges each participant in a base-stealing attempt for his likely effect upon its success. Using a generalized linear mixed model, we simultaneously weight all participants involved in attempted steals against each other, and then determine the likelihood of the base ending up as stolen, as compared to the involvement of a league-average pitcher, catcher, or lead runner, respectively.
(from http://bbp.cx/a/26195)
Stated another way, Swipe Rate allows us to evaluate how good Yadier Molina’s arm is while controlling for the inherent ability of his pitchers to hold runners and the quality of the runners he is facing on base. Likewise, we evaluate the ability of individual pitchers to hold runners while controlling for the possibility that they may be throwing to a catcher with a subpar arm. And for baserunners in particular, we now have something much more accurate to evaluate their base-stealing ability than base-stealing percentage.
Remember that base-stealing percentage, by itself, is not very useful: using straight percentages, an elite base-stealer who swipes 90 percent of his attempts and tries to steal 40 times a year ranks lower than a catcher who had one lucky steal all year (and therefore has a 100 percent base-stealing percentage). In the same way that Controlled Strikes Above Average (CSAA) controls for the effect of other factors on catcher framing, Swipe Rate Above Average regresses baserunners’ steal-success rates against both themselves and others to provide a more accurate assessment of each participant’s effect on the likelihood of a stolen base.
The factors considered by the Swipe Rate are:
- The inning in which the runner was on base;
- The stadium where the game takes place;
- The underlying quality of the pitcher, as measured by Jonathan Judge’s cFIP statistic;
- The pitcher and catcher involved;
- The lead runner involved.
Because the statistic rates pitchers above or below average in preventing stolen bases, average is zero, and pitchers generate either positive (bad) or negative (good) numbers. In 2014, here were the pitchers who were hardest to steal a base on:
A comprehensive Scoresheet valuation metric designed by Ben Murphy, as explained in this article.
(or SS/Sim) Runs above Replacement for Scoresheet Baseball (SS). This should also be helpful for other sim leagues. This statistic accounts for:
- Scoresheet defensive range ratings, and Scoresheet position eligibility
- Reliver leverage effects
- All-Star Effect (assuming 10 team AL league or 12 team NL league)
Stuff. A statistic developed by Clay Davenport that measures a pitcher's likelihood of success in the majors by analyzing his component rates.
Number of streaks of a particular length
Percentage of pitches thrown for strikes.
Saves.
Swing rate: the percentage of pitches swung at.
Swing rate is simply swings (either by hitters or seen by pitchers) divided by total pitches.
Hitter Examples (2012)
Very few: George Kottaras, 0.3319
Few: David Wright, 0.4260
Around average: Kevin Frandsen, 0.4604
Many: Manny Machado, 0.4892
Very many: Delmon Young, 0.5890
Pitcher Examples (2012)
Very few: Carlos Marmol, 0.3534
Few: Francisco Cordero, 0.4419
Around average: Matt Garza, 0.4596
Many: Craig Breslow, 0.4738
Very many: Junichi Tazawa: 0.5485
Swinging strike rate: percentage of swings missed.
Used to identify on which side the injury occurred.
The average number of end-of-season losses in the simulated seasons.
The average number of end-of-season losses in the simulated seasons. For in-season playoff odds, this number includes a team's actual losses along with the average number of losses from simulating the remainder of the season.
The average number of end-of-season wins in the simulated seasons.
The average number of end-of-season wins in the simulated seasons. For in-season playoff odds, this number includes a team's actual wins along with the average number of wins from simulating the remainder of the season.
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.
Beginning in 2006, BP has developed a proprietary version of Speed Score that takes better advantage of play-by-play data and ensures that equal weight is given to the five components. In the BP formulation of Speed Score, an average rating is exactly 5.0. The highest and lowest possible scores are 10.0 and 0.0, respectively, but in practice most players fall within the boundary between 7.0 (very fast) and 3.0 (very slow).
The "standard league" is a mythical construction, in which all statistics have been adjusted for easy comparison. Its primary features are that runs scored is 4.5 runs per game; equivalent average is .260; and the pythagorean exponent is exactly 2.00.
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 particular, for hitters:
'Superstar' performance represents an EqA of .300 or better.
'Star' performance represents an EqA of between .280 and .300
'Regular' performance represents an EqA of between .250 and .280
'Fringe' performance represents an EqA of between .230 and .250
'Scrub' performance represents an EqA worse than .230
'Drop' represents the player's Drop Rate - the probability that the player will drop out of the league entirely.
Note that these thresholds ARE adjusted for a player's defensive position. A shortstop would need an EqA of about .290 to be considered a 'Star' performer, while a right fielder would need an EqA of .310.
Similarly, for pitchers:
'Superstar' performance represents an EqERA of 3.25 or better.
'Star' performance represents an EqERA of between 3.25 and 4.00
'Regular' performance represents an EqERA of between 4.00 and 5.00
'Fringe' performance represents an EqERA of between 5.00 and 5.50
'Scrub' performance represents an EqERA worse than 5.50
'Drop' represents Drop Rate - the probability that the player will drop out of the league entirely.
A small adjustment is made for starters versus relief pitchers, analagous to the positional adjustment described above.
In PECOTA, stolen base attempts as a percentage of times on first base.
Strikeouts per plate appearance.
Number of strikes seen (batter) or thrown (pitcher)
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.
Saves + Holds
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