AdvancedOverall
WPA
Win Probability Added
The change in a team's chance of winning from before a play to after it, credited to the batter and pitcher involved.
0.0Average (by definition)
Simple explanation
A home run that breaks a tie in the ninth and one that comes with a ten-run lead don't weigh the same. WPA measures the difference in win probability.
If a team's chance of winning is 40% before a plate appearance and a double pushes it to 70%, the batter gets +0.30 and the pitcher −0.30. Add those up over a season for the player's WPA; +1 means one win more than average.
Benchmarks
- −3.0
- Very poor
- 1.0
- Typical regular
- 3.0
- Good
- 6.0
- Elite
Rough cutoffs for a regular over one season (FanGraphs rules of thumb). League average is 0 by definition.
Detailed explanation
WPA = win probability after the play − win probability before the play
Whatever the batter gains, the pitcher loses, so at the end of a game the winning team's players add up to +0.5 and the losing team's to −0.5. Defense isn't split out; it all goes to the pitcher, so position players' WPA moves only with their hitting and baserunning.
It measures how much a player's performance mattered, not how well he played. Players who get lots of big chances can pile up big totals in either direction. FanGraphs treats WPA as a number for telling the story of games and advises against using it to predict anything.
FanGraphs also splits a season's WPA into the sum of the good plays (+WPA) and the sum of the bad ones (−WPA).
Common misconception
“Players with a high WPA are clutch.”
A big WPA records that a player got lots of big chances and came through in them. There's little evidence that it's a skill that carries over from year to year.