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Glossary: Defense

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For hitters: Singles
For pitchers: Singles Allowed
For positions: First Baseman


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For hitters: Doubles
For pitchers: Doubles Allowed
For positions: Second Baseman


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For hitters: Triples
For pitchers: Triples Allowed
For positions: Third Baseman


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A player capable of playing the four corner positions: first base, third base, right field and left field.


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According to the MLB offical rules, an assist is "credited to a fielder whose action contributes to a runner being put out."


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Official plate appearances where the batter doesn't walk, get hit by a pitch, hit a recognized sacrifice or is interfered with by the catcher.


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Hitters: Base on balls (walks)
Pitchers: Base on balls (walks) allowed


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Double plays, turned or hit into.

Def Eff

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Def Eff, or Defensive Efficiency, is the rate at which balls put into play are converted into outs by a team's defense. Def Eff can be approximated with (1 - BABIP), if all you have is BABIP, but a team's actual Def Eff is computed with

1 - ( H - HR ) / ( AB - SO - HR + SH + SF )

the Team Audit Standings use the latter formula.

Alternately, it will be seen some places (including some past editions of Baseball Prospectus) computed as 1 - ((H + ROE - HR) / (PA - BB - SO - HBP - HR)), which comes out slightly lower in most instances.

Here is an example of the Defensive Efficiency spectrum based on the 2011 season:

Excellent - Tampa Bay .735
Great - Texas .722
Average - Toronto .710
Poor - Pittsburgh .700
Horrendous - Minnesota .693


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The biggest difference between Fielding Runs Above Average and similar defensive metrics comes in the data and philosophy used. Whereas other metrics use zone-based fielding data, Fielding Runs Above Average ignores that data due to the numerous biases present. Fielding Runs Above Average instead focuses on play-by-play data, taking a step back and focusing on the number of plays made compared to the average number of plays made by a player at said position. The pitcher's groundball tendencies, batter handedness, park, and base-out state all go into figuring out how many plays an average player at a position would make.

Here is an example of the Fielding Runs Above Average spectrum based upon the 2011 season-for the sake of consistency, the players featured below all play the same position (center field):

Excellent - Jacoby Ellsbury 11.6
Great - Nyjer Morgan 5.5
Average - Marlon Byrd 0.6
Poor - Roger Bernadina -5.2
Horrendous - Melky Cabrera -13.2

WARP components can be found in this article, which also describes 2015 changes to FRAA: http://www.baseballprospectus.com/article.php?articleid=27944


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Hits, or hits allowed.


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Not recorded for the NL 1876-1886, the AA in 1882-83, the 1884 UA, and the 1871-75 NA, for either hitters or pitchers.


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Home runs, or home runs allowed.


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Someone who can play both middle infield positions, second and short.


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Plate appearances; AB + BB + HBP + SH + SF.


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Based off of Bill James' Defensive Efficiency idea, PADE calculates how well a team performed on defense, while adjusting for their park environments. Certain parks make it easier for the defense to turn a ball in play into an out and this adjusts for that fact.

Introduced by James Click here and updated by Click here.

Here is an example of the Park-Adjusted Defensive Efficiency spectrum based on the 2011 season:

Excellent - Tampa Bay 4.30
Great - Los Angeles of Anaheim 1.47
Average - Atlanta -0.02
Poor - Chicago (A) -1.41
Horrendous - Minnesota -2.41


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Passed balls; not available for the NA.


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Player's position.


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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.


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Similar to Batting Average on Balls in Play, SLGBIP gives an impression of the damage done by the balls in play. As seen here.


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Strikeouts. For pitchers, batters struck out, for batters, times struck out.


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Triple plays

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