Yesterday, pulled some data for Eno Sarris on pitch type and groundball rates. He was looking for the average groundball rates for different pitch types. I stole a bit of the data and ran a query I have wanted to for a while: What is the average groundball rate difference for a pitcher who throws both two-seam and a four-seam fastball. For those who don’t know, a two-seam fastball has more movement than a four-season. And what I found was:
Pitchers will see a 9.5% point increase in their groundball rate when they throw their two-seam fastball compared to their four-seam fastball.