Expected Stats (xBA, xSLG, xwOBA)
Also known as: xwOBA, xBA, xSLG, expected batting average, expected slugging, expected woba, expected weighted on-base average, expected stats in baseball
XBA, xSLG and xwOBA are Statcast's expected stats. They estimate what a hitter's batting average, slugging and wOBA should be, based on how hard and at what angle each ball was hit. On some weakly hit balls, sprint speed is added. Because they remove the defense, they show contact quality better than the real results.
Each batted ball gets a value based on how often similar balls have become hits since Statcast began league-wide in 2015. Similar means a close exit velocity and launch angle. Since 2019, topped or weakly hit balls also use the batter's sprint speed.
Expected batting average (xBA) uses the chance of a hit. Expected slugging (xSLG) uses the chances of a single, double, triple and home run. Expected wOBA (xwOBA) uses the same hit values as wOBA, plus real walks, strikeouts and hit-by-pitches.
A hitter's real numbers can be higher or lower than expected because of defense and luck. MLB's glossary gives an example: Marcell Ozuna had a .327 wOBA in 2018, but his xwOBA was .359.
Tips by skill level
If your results are bad but you keep hitting the ball hard, your expected numbers are probably better than your real ones.
Look at the gap between wOBA and xwOBA over a full season. A big gap often shrinks over time.
Example
A hitter is batting .220, but his xBA is .290. He is hitting the ball hard and finding gloves. His coach tells him to keep his approach.
Why it matters
Expected stats separate what a hitter controls, contact quality, from what he does not. They help explain slumps and hot streaks.
Common mistakes
- Treating expected stats as a prediction that must happen
- Ignoring that strikeouts and walks are part of xwOBA
- Comparing small samples of a few games
Frequently asked questions
What is xwOBA?
It is expected weighted on-base average. Statcast estimates a hitter's wOBA from exit velocity and launch angle, plus sprint speed on some balls, instead of using the real results.
What is xBA?
It is expected batting average. Each batted ball gets a hit chance based on how often similar balls became hits, and strikeouts are added in.
Why is my xBA higher than my batting average?
Your contact quality is better than your results. Defense or bad luck has taken away hits that similar balls usually get.
Sources
Related terms
- Weighted On-Base Average (wOBA)Weighted On-Base Average (wOBA) gives each hitting outcome a run value. It combines walks and hits into one rate that is scaled like on-base percentage.
- Exit Velocity (EV)Exit velocity is how fast the ball comes off the bat, in mph. It is a ceiling metric — the harder you hit it, the farther it can go.
- Launch Angle (Batting)Launch angle in batting is the vertical angle the ball leaves the bat. Roughly 10–25° produces the hardest, most productive contact.
- BABIP (Batting Average on Balls in Play)BABIP is batting average on balls in play: hits that are not home runs, divided by the balls a hitter puts in play. The formula is (H − HR) ÷ (AB − K − HR + SF). League average is almost always around .300. Line drives fall for hits more often than ground balls, and ground balls more often than fly balls. As a result, hard line-drive contact helps. But short streaks are mostly luck.
- Batted Ball Event (BBE)A batted ball event is any batted ball that produces a result: a hit, an out or an error. Every fair ball counts, and so does a foul ball caught for an out. Other foul balls do not count. Statcast uses batted ball events to figure average exit velocity, launch angle, hard-hit rate and barrel rate.
Related guides & benchmarks
Work on the cause
Video shows how you move, not the ball itself. Film one swing to find the movement behind this result — free to start.
See a sample Baseball report first