# Plate Discipline Correlations for Pitchers.

I decided to go back to researching pitcher strikeout correlations today, which has been one of my favorite topics of research lately. Now that I have MINITAB, I can generate this stuff a little easier. The interface is nice as well. So, here are a few graphs and correlations. Again, same rules as before: qualified pitchers from 2008.

Today we’ll look at some strong correlations and the regression equation I produced for projecting strikeouts.

First, here’s the graph for actual strikeouts versus the regression equation. It’s R-squared is .84.

It was generated using Fangraphs.com’s plate discipline statistics. There are a few interesting points. The two I liked most were the highest expected strikeouts (C.C. Sabathia: .2659 exp. K percentage, versus .2455 actual K%) and the highest actual strikeouts (Tim Lincecum, .2399 expected K%, .2858 actual K%). Lincecum’s outlandish strikeout totals make him an easy pick for an outlier or a player with substantial error.

However, I have a suspicion that the regression line for this problem would fit better as a non-linear relation.

Here are some other correlations that were pulled out of the data. Each correlation is the R value between the given variable and actual strikeout percentage.

Contact Percentage: -0.869

This one took the cake… and not surprisingly, either. If you miss bats, you will get lots of strikeouts. No surprise here.

Swing Percentage: 0.177

This one was a little surprising. I expected the correlation to be much stronger. If you swing more, you will make contact in more at-bats. The correlation is still there, but it is very weak. I would like to investigate this one a little more.

Zone Percentage: 0.065

To me, this one was shocking. I expected there to be at least some meaningful correlation between zone percentage and strikeout percentage. However, if seems that, for the range of zone percentage thrown among MLB pitchers, there is no correlation. Of course, a pitcher who never throws strikes will never strike anyone out, but, for the range that MLB players throw strikes, it makes no difference. If you want to avoid BBs, pound the zone. If you want strikeotus, I guess it doesn’t matter much.

O-Swing: 0.323

This was another surprising development. I expected this to be much higher: if you can get a batter to chase pitches, he’ll miss more often. The logic is certainly true, but, again, for the range of values among MLB pitchers, there is a weak correlation. Don’t get me wrong, it does matter, just not as much as I had expected.

ZSwing %: -0.052

Another surprise. This may have further implications to the ability of pitchers to get called strikes. The amount that a hitter swings in the zone matters very little and is negligible. Wouldn’t it seem that a hitter who swung a lot in the zone would make contact more and strike out less? Guess not. Funny how things are sometimes.

That’s all for now. Next time, we’ll continue this study of plate discipline statistics