Win probability added
also: WPA
How much a single play moved a team's chance of winning that specific game — the change in win probability, play by play.
WPA = win probability after the play - win probability before itWin probability is a function of score, time, field position, down and distance. WPA is its change across one play, so every play in a game sums to the winner going from its opening number to one, and the plays that moved it most were the ones that decided it.
It answers a different question from EPA. EPA asks how good a play was; WPA asks how much it mattered. A nine-yard gain on first quarter first down has real EPA and almost no WPA. A one-yard sneak on fourth and goal with a minute left has modest EPA and can be the largest WPA of the season.
That makes it the right tool for describing a game and the wrong tool for rating a player. Leverage is not evenly distributed, and a quarterback on a team that plays close games accumulates WPA that a better one on a team winning comfortably never gets the chance to.
Ranking seasons by total WPA. It rewards being in close games, which is mostly not a skill; rank by EPA and use WPA to explain what happened.
Where to get it
Related
Win probability added from the API
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