# Strikeout Percentage

A player’s strikeout expectancy is among the most important parts of his value. A player that strikes out frequently has a short career ahead of him, unless he can walk and hit homeruns like Jack Cust. Lots of strikeouts means few opportunities to put the ball in play, which means a lower batting average, fewer home runs, and more losses. Take a look at the annual batting average leaders, you’re likely to find few players who strike out with high proclivity.

But, as with anything else, strikeouts are subject to randomness and statistical noise. This begs the question, how many strikeouts is a player expected to have given certain plate discipline characteristics?

To shed some light on this question, I created a simple regression equation, regressing contact percentage and swing percentage against strikeout percentage, using batting statistics from the 2008 season. The r-squared of the equation was .8719, meaning that even regressing just these two variables yields a relatively accurate outcome.

As always, there are other considerations to think about, such as how often a player swings out of the zone, in the zone, how often they make contact with these pitches, and 2-strike contact percentage, among others.

But I digress. Below are some of the results of the equation. “Unlucky” hitters are those who struck out more than expected. “Lucky” hitters should have struck out more than they did according to the equation.

Unlucky Hitters

 2008 K% Ex K% Difference Swing % Contact % Gregor Blanco 0.23 0.1628 0.0672 0.4 0.862 Adam LaRoche 0.248 0.1965 0.0515 0.442 0.813 Fred Lewis 0.265 0.2147 0.0503 0.43 0.8 Pat Burrell 0.254 0.2053 0.0487 0.42 0.813

Lucky Hitters

 Troy Glaus 0.191 0.2447 -0.0537 0.396 0.784 Russell Martin 0.15 0.1906 -0.0406 0.4 0.835 Lance Berkman 0.195 0.23228 -0.03728 0.466 0.769 Curtis Granderson 0.201 0.23361 -0.03261 0.393 0.796

Close Projections

 Johnny Damon 0.148 0.1492 -0.0012 0.416 0.869 Derek Jeter 0.143 0.1444 -0.0014 0.482 0.848 Miguel Cabrera 0.205 0.2065 -0.0015 0.515 0.775 Raul Ibanez 0.173 0.1749 -0.0019 0.465 0.825

More investigation is necessary, especially the consistency of these plate discipline statistics and their implications on future performance. However, there are a few conclusions that can be drawn from this data.

The relatively low values of the standard errors show that total strikeouts are a pretty good indicator of how often a batter should strike out. Also, the observed errors indicate that other variables need to be considered, such as 2-strike contact percentage and other plate discipline statistics (i.e. O-Swing).

However, this simple 2-variable model is a good predictor of actual strikeouts and is a good tool for analyzing a player’s value.

Thanks to Fangraphs.com for their contributions to this article.

Regression calculations performed by:

Wessa, P. (2009), Free Statistics Software, Office for Research Development and Education,
version 1.1.23-r4, URL http://www.wessa.net/

Mike Silver recently completed his requirements for the Sport Management Major at THE University of Massachusetts-Amherst, where he is a brother of Theta Chapter of Theta Chi Fraternity, the best house in the country. He is a huge Red Sox and Bruins fan, and longs for the days of the REAL Boston Garden, Cam Neely, and the ultimate Dirt Dog Trot Nixon. If you have any questions, you can reach him at mjasilver@gmail.com. Have a good night readers, and know that Mike hopes to hear from you soon. If you quote Mike in an article, please let him know. He’d love to hear it.

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### 2 Responses to Strikeout Percentage

1. MattyD says:

Would you post the regression equation? I was hoping to see David Wright on that ‘unlucky’ list since his contact% is higher than average and his swing% is lower, but his K% is obviously way up this year. I’d love to see how he fares here.

2. sieyin says:

What are the right words … super, great idea