Entering Wednesday night’s game against the Yankees, Jackie Bradley Jr. was just 5-for-34 with a wRC+ of 25. He went 3-4, raising his average to .206 and his wRC+ to 58. Even though he’d been off to a slow start, Statcast indicates that he’d actually been hitting the ball significantly better than that .133 average suggests.
We can compare all batted balls hit with similar launch angles and exit velocities over the past three seasons to get a hit probability for each batted ball. We can also use the probabilities of specific outcomes such as singles, doubles, triples and home runs to get an expected slugging percentage (xSLG) for each batted ball as well as a total cumulative xSLG. With large enough sample size, xSLG generally converges to SLG. Baseballsavant.com, a website containing the publically available Statcast data, calls this difference xSLG-SLG. A player whose statistics accurately convey the balls he hits would have an xSLG-SLG of 0.
In 2017, Jackie Bradley had an xSLG-SLG of .007, a margin of error of approximately 1.7 percent. In 2017, his slugging percentage conveyed a mostly accurate picture of the balls he hit over the course of the season.
Through the extremely small sample size of his first eight games, Jackie Bradley had an xSLG-SLG of .179. His actual SLG was .200 but his xSLG was almost exactly double that. Every player goes through a stretch of hitting balls hard but right at people. Lineouts are good contact with no reward. We’re told they all balance out over the course of the season, but so far Jackie Bradley has been getting very unlucky.
For example, let’s look at April 7 against the Rays. The box score will tell you that he went 0-for-4 and dropped his average to .115. He absolutely crushed two balls. One was a lineout to second baseman Joey Wendle. He hit it 105 mph at a launch angle of 10 degrees. That’s the kind of contact a hitter dreams of, and for good reason. Since 2015, MLB hitters are batting .912 on those balls. Yes, .912.
The other ball he squared up left his bat at 101.5 mph at 35 degrees. The fine print says it was a fly out to right fielder Mallex Smith. The fine print does not say that batters are hitting .646 on that type of contact and 58 percent of the time balls hit that well go for home runs.
He’s making good contact and it’s not surprising that he broke out last night against the Yankees. Yes, his numbers are off to a slow start. But they’ll catch up.