Graphing BABIP Against Speed

Faster players get more hits on their ground balls. That should be no surprise. There is a benefit to having speed in that you can beat more infield hits than slower players. That’s a fairly straight forward assertion, but ultimately I was a bit surprised that the gap is actually quite small.

I included the formula and fit from a linear fit. Looking at various other curves, none were demonstrably better. First, you can see that this is no strong correlation. Having a higher speed score offers some apparent benefit, but by no means is it a guarantee.

While there is a clear upward trend since the focus in on just a fraction of a fraction, there macro-level differences aren’t that massive. Over 150 ground balls, which is a roughly average number per season for the average player, the difference between a 10th percentile speed score (2.2) and a 90th percentile speed score (6.9) comes out to just four hits.

There are outliers to be sure. That very noticeable dot at the top is Matt Kemp‘s 2007 season when he posted a .442 BABIP on 104 ground balls. On the bottom rung is Eric Hinske’s 2003 mark of a .105 BABIP on ground balls despite a speed score that year of 6.0.

As mentioned in the introduction, the general trend of BABIP on ground balls rising as players get faster is no shock. That is probably what anyone would have guessed, but I had yet to see it verified in the data this way. Go forth now and speak with slightly more conviction when the topic is broached.