With MLB’s recent decision to enforce their foreign substance rule regarding pitchers, many are expecting a decrease in spin rates. While most of the focus is on how this will affect pitchers, I decided to focus on hitters that may benefit the most from this crackdown.
It is very difficult to say exactly how much spin rates will drop. How much will the rule actually be enforced? Who is using what? Some pitchers will inevitably be able to avoid detection. Certainly, a percentage of the increasing spin rates we’ve seen is due to things other than foreign substances. The use of different technologies like high-speed cameras has led to slightly different grips, arm motions, etc. that can increase spin.
With so much uncertainty it didn’t make a whole lot of sense for me to get overly scientific with my methodology. Using Baseball Savant, I found the 90th percentile spin rate for four-seamers, two-seamers, cutters, sliders, and curveballs, respectively. I then queried hitters for 2020-2021 that have faced at least 10 pitches from each type that had a spin rate above that 90th percentile. I then selected all hitters where at least 20% of the total pitches they faced were of these 90th percentile varieties and the wOBAs were less than .250. All of these cutoffs were chosen rather arbitrarily, but it seems like a decent bet that these highest spin pitches will be greatly reduced in the near future.