In baseball’s endless search for new ways to measure the game, we’ve recently seen the development of WPA. Using historical data, it tracks the odds a team has of winning a game at any given time, based on run differential, outs, and base situation. It has its flaws, but it does serve one purpose: it captures the essence of a game. Tom Tango examines this using a painful example, Ichiro’s walk-off. With two outs in the bottom of the ninth, WPA gave the Yanks an over-95-percent chance to win the game. Mike Sweeny’s double reduced that to 85.8 percent, and Ichiro made up all the difference. Tango also notes the general fan reaction, which makes sense after such an improbably turn around.
This feeds in nicely with the discussion in the Dominance Factors thread. The purpose of WPA is not to evaluate a player’s performance. It is to show the ebbs and flows of a game. Used for this purpose, it’s a wonderful stat. Used for others, it can mislead.
By request, the graph from that night:
From FanGraphs.
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