Prospect Scouting & Stats — Pitcher Pitch Grades & Strikeout Rate Part 2

Yesterday I began diving into prospect pitch grades and strikeout rate. Today, I’m going to share correlations with some additional pieces of data we might want to use to help project a prospect’s strikeout potential.

As I was deciding what to publish for today’s post, I realized that I remembered seeing velocity on the scouting grade tables on THE BOARD, but they weren’t on the Scouting & Stats tab so I forgot about them. Lo and behold, if you click back to the Scouting Only tab and then click Scouting – Pitching, we find four more pieces of data ripe for correlating with strikeout rate. So let’s do it.

Pitch Characteristic Correlations
K% SwStr%
RPM FB* 0.19 0.07
RPM Break** 0.08 -0.03
Sits – Low 0.22 0.00
Sits – High 0.20 -0.05
High-Low Range -0.06 -0.11
Tops 0.14 -0.09
*Average fastball spin rate
**Average spin rate of primary breaking ball

And now sorting correlations with strikeout rate in order of absolute value, from strongest to weakest. Once again, correlations with SwStk% were very weak, so we’ll ignore them.

Pitch Characteristic Correlations w/K%
Sits – Low 0.22
Sits – High 0.20
RPM FB* 0.19
Tops 0.14
RPM Break** 0.08
High-Low Range 0.06
*Average fastball spin rate
**Average spin rate of primary breaking ball

It’s a good thing I remembered these additional variables, because they are actually meaningful. I decided to break up the “Sits” value into the low velocity and high velocity, and not surprisingly, those two have the strongest correlation with strikeout rate. We’ve always known that all else equal, higher velocity results in a higher strikeout rate.

Next and sitting just behind the top end of the velocity range is RPM FB, which is average fastball spin rate. We’ve been hearing a lot more about spin rate in recent years now that the data is available. This correlation, although not super strong, is positive and meaningful. A higher spin rate fastball correlates somewhat with a better strikeout rate in the minors. The RPM also influences the FB – Present grade, even if our graders weren’t actually using it to come up with their grade. The correlation between FB – Present and RPM FB was 0.15, which isn’t great, but not nothing.

The “Tops” value represents the pitcher’s maximum velocity and it’s always fun to peruse the leaderboard (we’ll get to that in a future post). It also sports a double digit correlation with strikeout rate, but it’s not as strong as the two Sits values. About 62% of prospects top out at two MPH greater than their Sits – High value, while 25% top out at one MPH more. The rest top out between three and five MPH greater (the five must be a mistake!).

Finally, we get to our first single digit correlation from RPM Break. This is the average spin rate of whatever the prospect’s primary breaking ball is. Apparently, it doesn’t mean a whole lot when it comes to predicting strikeout rate. You’re better off simply looking at the pitch grades as the SL – Present and CB – Present grades sport significantly stronger correlations.

Last, I thought it would be interesting to find out if the range between low and high velocity mattered at all. Do larger ranges correlate with higher strikeout rates and vice-versa? The correlation is quite small, and although still positive, I’m hesitant to claim that a bigger velocity range results in a higher strikeout rate. Given the low correlation and not-massive sample size, it’s safer to ignore the velocity range.

We hoped you liked reading Prospect Scouting & Stats — Pitcher Pitch Grades & Strikeout Rate Part 2 by Mike Podhorzer!

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Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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