R-Squared Fun with BB% and SO%

by
November 17, 2009

Some have expressed interest in the r-squared values for common metrics like walk and strikeout rates for starting pitchers. With that in mind I took each of the pitchers with at least 100 innings pitched in 2008-9 and ran their BB% and SO%. This gave us a sample of 92 pitchers and some numbers that are pretty similar all told.

Here’s the graph with important information for walk rate:

ytybb

And here for strikeouts:

ytyso

Minimal difference. Both are skills, albeit not 100% so. The more interesting aspect from the data set is the biggest droppers and risers for each. Jon Lester saw his strikeout rate rise from 17.4% to 26.7%; Justin Verlander from 18.5% to 27.4%; Joe Blanton from 13% to 19.5%; Matt Garza from 16.6% to 22%; others who jumped at least five percentage points include Adam Wainwright, Clayton Kershaw, and Zack Greinke. The biggest droppers for Ks were Joba Chamberlain (-9.5%), Scott Kazmir (-7.8%), Ervin Santana (-6.4%), Micah Owings (-6.1%), and Bronson Arroyo (-4.9%). Something must be in the Angels water bottles.

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As for walks. Verlander again excels at something good and saw his walk rate decline 3.5%; Barry Zito and Ubaldo Jimenez saw 2.6% drops; Ted Lilly and Ubaldo Jimenez round out the top five with 2.3% drops and Felix Hernandez experienced the sole other 2% drop. Kyle Davies had his walk rate climb 3.5%, Livan Hernandez and Owings (ouch) 3%, Andy Pettite 2.9%, and finally Santana and Todd Wellemeyer had their walk rates go up 2.5%.

For those who love consistency, Jake Peavy, Lester, and Nick Blackburn saw zero movement in their walk rates and Lilly held the same distinction with his strikeout rate.





 

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Lee TrocinskiMember since 2016
16 years ago

First, what season is what axis? I would assume ’08 is the x-axis and ’09 is the y-axis. Second, it’s interesting that the slope of both regression lines is well below 1. K% went up .5% league-wide, so a .76 slope is very surprising. I know pitchers’ K rates generally drop throughout their career, but not that much in one season. BB rates went up .2% league-wide, so a .8 slope seems a little extreme also.

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Lee TrocinskiMember since 2016
16 years ago
Reply to  Lee Trocinski

I just figured out that the regression line actually shows regression towards the mean. (who woulda thunk?) I forgot to factor in the intercept in my initial analysis.

Unrelated, I wonder if league changes really affected the results that much. Other than Blanton, who already had a third of a season with PHI last year, no other league changing pitchers up there, one way or another.

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