These brief definitions were created with the help of Steve Slowinski and The Sabermetric Library
. For much more in depth explanations of these statistics, be sure to check out this invaluable resource.
+/- – Dewan Plus-Minus
Invented by John Dewan. Determines via positive and negative percentage points, how many more or fewer successful plays a defensive player will make compared to a league average counterpart.
ARM – Outfield Arm Runs
The amount of runs above average an outfielder saves with their arm by preventing runners to advance.
BABIP – Batting Average on Balls in Play
This measures how many hits are collected in relation to all of the balls a hitter puts in play. League average is between .290 – .300.
Contact% – Contact Percentage
The overall percentage of pitches a batter makes contact with when swinging the bat.
DPR – Double-Play Runs
The amount of runs above average an infielder is in turning double-plays.
ErrR – Error Runs
Calculates whether a player commits less or more errors compared with a league-average player at his respective position.
FB% – Fly Ball Percentage
Ratio of fly balls batted to total number of balls put in play.
FIP – Fielding Independent Pitching
The number of earned runs per nine a pitcher would have given up if performance on balls in play and timing were assumed to be league average.
GB% – Ground Ball Percentage
Ratio of ground balls batted to total number of balls put in play.
HR/FB – Home Runs per Fly Ball
The percentage of how home runs a player hits out of the total number of fly balls they hit.
ISO – Isolated Power
This removes all the singles that are included in SLG% (SLG% – BA) and leaves us with a measure of a player’s total power numbers.
LD% – Line Drive Percentage
Ratio of line drives batted to total number of balls put in play.
LI – Leverage Index
Describes if a player has been used in high, medium, or low leverage situations and is no way a predictive statistic.
LOB% – Left on Base Percentage
Measures the percentage of base runners that a pitcher strands on base over the course of a season. League average is around 70-72%.
O-Contact% – Outside Contact Percentage
The percentage of pitches a batter makes contact with outside the strike zone when swinging the bat.
O-Swing% – Outside Swing Percentage
The percentage of pitches a batter swings at outside the strike zone.
OPS+ – On-base Plus Slugging Plus
Compares a players OPS to league average (league average is 100). This statistic is park and league adjusted.
RngR – Range Runs
Calculates whether a player gets to less or more batted balls compared with a league-average player at his respective position.
Spd – Speed Score
Statistic developed by Bill James that attempts to rate how fast a player is.
Swing% – Swing Percentage
The overall percentage of pitches a batter swings at.
tERA – True Earned Run Average
The exact same as tRA, but scaled to ERA.
tRA – True Run Average
A fielding independent pitching metric that takes into account batted ball types as well as strikeouts, walks, and home runs, and assigns expected run and out values to them. It is on a R/9 scale.
UZR – Ultimate Zone Rating
UZR puts a run value to defense, quantifying how many runs a player saved or gave up. Categories compiled into the stat are Arm, DPR, RngR, and ErrR.
WAR – Wins Above Replacement
Essentially the number of wins (10 runs = 1 win) a player is worth compared to his replacement. Calculated for offensive players using wRAA and UZR and for pitchers using FIP. The stat is context, league, and park neutral.
wOBA – Weighted On-Base Average
Combines all aspects of hitting into one metric while weighting them in proportion to their actual value. Includes non-intentional walks, hit-by-pitches, singles, reached on error, doubles, triples, and homeruns.
WPA – Win Probability Added
Measures how an individual player affects his team?s win expectancy on a play-by-play basis.
WPA/LI – Context Neutral Wins
By dividing WPA by LI, one sees how much value a player provided regardless of the leverage. WPA/LI is calculated over the course of a season for every at bat and is then summed at the end of the season.
wRAA – Weighted Runs Above Average
Calculates the number of runs a player contributes to their team above what an average player would contribute. Used to represent offensive ability in the WAR formula.
wRC – Weighted Runs Created
Measures how many total runs a player was worth over a time period based off of that player’s wOBA.
wRC+ – Weighted Runs Created Plus
Compares a player’s wRC with league average (league average is 100). This statistic is park and league adjusted.
xFIP – Expected Fielding Independent Pitching
Expands on FIP in realizing that there is a luck factor in a pitchers HR/FB rate and therefore removes the HR from the equation.
Z-Contact% – Zone Contact Percentage
The percentage of pitches a batter makes contact with inside the strike zone when swinging the bat.
Z-Swing% – Zone Swing Percentage
The percentage of pitches a batter swings at inside the strike zone.
Zone% – Zone Percentage
The overall percentage of pitches a batter sees inside the strike zone.