Breaking Down BABIP: What Impacts Ground Ball Batting Average for Hitters?

In rounding out my series on the most important factors influencing components of BABIP, I will be looking into what most affects a hitter’s batting average on ground balls. So far, the results of these analyses have been consistent. Launch angle has been the main driver of BABIP for pitchers, and it has been for hitters as well, at least when they are launching flyballs. The story is a different one, though, when hitters put the ball on the ground. Ground ball launch angle was not a significant factor in determining a hitter’s ground ball batting average, and neither was ground ball exit velocity.

Whether or not a hitter pulls grounders has much to say about whether that player will hit for average on grounders. There is a negative relationship between these variables that is significant at p < .0001 and with a Pearson’s r of .27. Even more important is how fast the hitter is. The Pearson’s r for the positive correlation between average sprint speed and ground ball batting average was .45.

That relationship is depicted in the graph below, and despite the strong relationship, it’s apparent that several hitters have managed to record ground ball batting averages that are far out of sync with what we would expect if we were only looking at their average sprint speed. Last year, Yoán Moncada and Marcell Ozuna were two of the biggest anomalies in terms of ground ball batting average that we have seen over the last five seasons, and I’ll explore the implications of that a little further below.

Looking at least season’s average sprint speed has predictive value when trying to project a hitter’s batting average on grounders (and overall batting average) for the coming year. When hitters have a ground ball batting average that diverges from what we would expect it to be based on their average sprint speed, it typically regresses in the next season in which they hit at least 150 grounders. There is a relationship between a hitter’s degree of overperformance on ground ball batting average (as a function of average sprint speed) and the degree to which their ground ball batting average drops in the next season with 150-plus grounders, and the correlation is significant at p < .0001 with a Pearson’s r of .62.

That means that hitters like Moncada, Ozuna and others who were at the extremes of over- or under-performing their expected ground ball batting averages in 2019 are likely due for a notable change in batting average in 2020. Miguel Rojas, Adam Eaton and Yolmer Sánchez all had ground ball pull rates below 45 percent last year, which was far below the major league average of a 55.5 percent, so they could be exceptions to this pattern. Even though they show up as having overperformed, they may “overperform” again in 2020, and that could be especially welcome news for Eaton, who actually slumped to a .279 overall batting average. Joining the flyball revolution did nothing for his power numbers, so if he eschews flies for grounders again, he could hit .290 or higher without sacrificing homers. For hitters like Moncada, Nolan Arenado and Kolten Wong, some regression in ground ball batting average is to be expected.

For Moncada, that is no big deal, as most fantasy owners are likely baking some regression from a .406 overall BABIP into their expectations. Arenado’s .319 ground ball batting average was by far his highest during the Statcast era, but his .312 overall BABIP was right in line with recent marks. Unless he has a second consecutive season with a below-average line drive rate (it was 19.3 percent in 2019), regression to his ground ball batted average should not impact his overall numbers. Kolten Wong’s .308 average on grounders should alarm anyone who was planning to draft him on the basis of last season’s stats. He did not get speedier, and he actually got pull-heavier on grounders, so he looks like a prime candidate for serious regression from his overall .285 batting average.

Ozuna (65.6 percent pull rate), Max Kepler (70.3 percent) and Kole Calhoun (69.2 percent) got extremely pull-happy with their grounders, so we can’t count on any of them to be .260 hitters this season. That is particularly worrisome for Ozuna, who is pegged by all of the major projections systems for a batting average in the .270s or .280s. Conversely, C.J. Cron and Jurickson Profar could surge in batting average this year.

If Albert Almora Jr. manages to earn significant playing time, 2020 could be a breakout season for him. He deserved much better than a .205 batting average on grounders in 2019, especially since he pulled only 46.3 percent of his ground balls. Almora hit more grounders than ever, setting a career high with a 53.1 percent rate, but he also posted a career-high 15.4 percent HR/FB and blasted 12 home runs in only 363 plate appearances. His role for the coming season is uncertain, but a .280 batting average with double-digit home runs is a possibility if the season gets underway by some point in May. Almora just might be a safer bet than Alex Verdugo (228 NFBC ADP) to put up those numbers.