WPA
Win probability added — how much a single play moved the win-expectancy needle.
What WPA means
A walk-off HR can be +0.50 WPA; a strikeout in mop-up time is barely 0.01. Sums across a game show who actually swung the result.
What counts as a good WPA
Higher is better — roughly -.050 is poor, 0 average, .050 good, and .100 or better elite.
Also written
win_probability_added