The way baseball has evaluated fastballs is rapidly changing. Since the introduction of Spin Rate and Spin Efficiency, we now have a way to show that not all fastballs of similar velocities are created equally. When used properly these can be great for helping a pitcher determine where in the zone his fastball can be most effective. Michael Augustine wrote more about this in his article “Going Deep: The Four-Seam Fastball X-Factor”. My focus however is more on the why. Why are some pitchers able to generate so much more spin than others?
In general velocity is a pretty good predictor of spin rate. However, it’s not always the case that the guys who throw the hardest also have the highest spin rate. For example in 2019 Mike Minor had an average spin rate of 2650 RPMs on his fastball, ranking 4th in the majors. That very same pitch came in at an average of 92.5 MPH, ranking him 337th in average velocity. Similarly, Sonny Gray’s fastball came in at an average of 93.3 MPH and 2527 RPMs ranking him 284th and 25th respectively. On the other side of the spectrum are guys like Noah Syndergaard and Jordan Hicks, notable sinker throwers.
|Player||Velocity (mph)||Rank||Spin Rate (rpm)||Rank|
In order to account for velocity’s impact on spin rate, Bauer Units are a fantastic way to tell how hard a pitcher spins the ball relative to how hard they throw. Bauer Units are calculated by simply dividing the spin rate of the pitch by the velocity. As stated earlier, velocity has been found to be a pretty solid predictor of spin rate, which means we might expect everyone’s Bauer Units to be roughly the same since we expect to see spin rate increase with velocity. However, the guys I’ve pooled here, as well as many others, clearly don’t follow that trend.
|Player||Bauer Units (rpm/ mph)|
Many articles of this flavor have been written in the past, and what I’ve found amongst most of them is that Bauer Units are an inherently difficult thing for a pitcher to increase. One thing that I feel hasn’t been explored enough in this area is how a pitcher’s grip could affect these numbers. Four-Seam fastballs are considered the fastballs which generate the highest spin rate, but aside from that not much else has been looked at in terms of specifics about exact grip. A lot of this can be explained by Four-Seam fastball grips, for the most part, being very uniform. However minute differences in grip I suspect could help pitchers stay behind the ball longer.
Another huge contributor to a fastballs flight characteristics is that of spin efficiency. Spin efficiency is a way to measure the percentage of raw spin that directly impacts movement. Spin efficiency is a great indicator of why sometimes guys with a lower raw spin rate can still generate similar movement to guys with much higher spin rates. Josh Hader is an excellent example of this and I’d highly recommend checking out this article written by Trevor Powers for more information.
This is why I’ve set out to calculate those fine differences through BallR and will post my updates here on the BCBlog.