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.

2019 Avg and xAvg on Ground Balls
Player GB Avg xGB Avg Difference
Yoán Moncada 0.373 0.264 0.109
Yolmer Sánchez 0.357 0.263 0.094
Nolan Arenado 0.319 0.240 0.079
Miguel Cabrera 0.274 0.209 0.066
Adam Eaton 0.335 0.271 0.064
Miguel Rojas 0.300 0.246 0.054
Kolten Wong 0.308 0.262 0.046
Wilson Ramos 0.244 0.201 0.043
Freddy Galvis 0.282 0.240 0.042
Jonathan Villar 0.307 0.266 0.041
Andrelton Simmons 0.286 0.245 0.041
Yasiel Puig 0.310 0.270 0.040
Yasmani Grandal 0.258 0.218 0.040
Freddie Freeman 0.206 0.246 -0.040
Christian Vázquez 0.193 0.237 -0.044
Adam Frazier 0.211 0.257 -0.046
Eddie Rosario 0.209 0.255 -0.046
Josh Bell 0.202 0.250 -0.048
Eduardo Escobar 0.212 0.262 -0.050
Nick Markakis 0.190 0.242 -0.052
Randal Grichuk 0.213 0.268 -0.055
Kevin Kiermaier 0.224 0.285 -0.061
Nick Ahmed 0.205 0.270 -0.065
Albert Almora Jr. 0.205 0.272 -0.067
Max Kepler 0.195 0.263 -0.068
Kole Calhoun 0.167 0.240 -0.073
C.J. Cron 0.167 0.242 -0.075
Jurickson Profar 0.169 0.250 -0.081
Marcell Ozuna 0.160 0.259 -0.099
SOURCE: Baseball Savant
Min. 150 ground balls. xAvg on ground balls calculated from regression equation where x = average sprint speed.

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.





Al Melchior has been writing about Fantasy baseball and sim games since 2000, and his work has appeared at CBSSports.com, BaseballHQ, Ron Shandler's Baseball Forecaster and FanRagSports. He has also participated in Tout Wars' mixed auction league since 2013. You can follow Al on Twitter @almelchiorbb and find more of his work at almelchior.com.

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jay_stellmachmember
2 years ago

Thanks for the great series of articles, Al — it is useful to have all of the general league-wide tendencies broken down like this as a way to try to predict some BA regression for some mid- and late-round hitters I have been eyeing (just drafted CJ Cron in my home league; not based on this, but it is nice to know that in addition to his play ing through injury last year, he may also have had some bad BABIP luck on grounders).

peterj
2 years ago
Reply to  Al Melchior

Al – I am not sure how you concluded that launch angle and exit velocity had little effect on batters batting average on ground balls but I must disagree. Using statcast data for2019 batters had a batting average of .166 on gbs hit with a launch angle of less than 0 degrees (40767 GB). For the 13108 GB hit with a launch angle between 0 and 10 degrees the BA was .357. Although average exit velocity did not very much on gbs hit between -10 and 10 degrees when grouped at 5 degree increments (87.3 to 92.3 mph), the results varied substantially. For instance, the .357 average mentioned above between 0 and 10 degrees LA breaks down to .440 for balls hit above 90 mph and .236 for balls hit below 90 mph.