Win Probability Added (WPA)



As an example: When Josh Donaldson came to the plate in the bottom of the ninth on May 26, 2015, the Blue Jays trailed by two and had men on second and third with no one out. That gave them a 43-percent win expectancy. After Donaldson's walk-off homer, their win expectancy jumped to 100 percent. Because Donaldson boosted the Blue Jays' chances of winning by 57 percent, his WPA for that plate appearance was 0.57.


The formula

(Team's win expectancy after a plate appearance or SB/CS/PK) - (team's win expectancy before that plate appearance or SB/CS/PK).


Watch: George Springer increases his WPA by 0.83 with a two-out, walk-off homer in the bottom of the 13th inning.

Why it's useful

WPA should not be used as an indicator of future performance. But WPA is a fantastic "story stat" -- meaning it does a good job of putting context to what has already happened. Its best use is for deciphering the impact of a specific player or play on a game's outcome.

Fantasy advantage

There are much better ways to better judge a player's skillset than by using his WPA. It's a metric based largely on situation, and it generally shouldn't be used for fantasy purposes.