xBA, xSLG, xwOBA: what deserved to happen
Rebuild a hitter's whole stat line using only the quality of his contact. What would it say?
For every batted ball, Statcast knows the EV and LA — and from a decade of data, the historical outcome odds of exactly that contact (105 mph at 20° ≈ .750 xBA, etc.). Sum the probabilities over a season and you get expected stats: the line the hitter earned, with fielders and luck averaged out.
The x-family
xBA rebuilds batting average; xSLG rebuilds slugging; xwOBA rebuilds wOBA — using real strikeouts and walks plus expected contact outcomes. That makes xwOBA the closest thing to one number for 'how well is he actually hitting' — Level 3's best stat with Level 4's measurement inside.
The percentile sliders on every StatLab player page lead with these. A .400 xwOBA hitter batting .240 isn't slumping — he's being robbed, and the numbers can finally prove it.
How this stat lies to you
- No spray direction or speed: fast slap hitters beat their xBA legging out grounders; slow sluggers into the shift undershoot, chronically.
- Park-blind — a Yankee Stadium short-porch homer and a Death Valley flyout can share an xSLG.
- 'Expected' means 'averaged over history', not 'destined' — gaps can persist for skill reasons.
Check yourself
1. xwOBA is built from…
2. Whose xBA will most chronically OVERstate his real batting average?