More Velocity and K/9 Charting

by
February 17, 2009

After this afternoon’s graph, some of you requested a breakdown by starters and relievers to remove any potential bias among soft-tossing relievers getting inflated strikeout rates due to their situational usage. So, here you go – I broke the group presented in the first graph into greater than 100 IP and less than 100 IP, which is a good enough proxy, and redid the graphs.

startervelo1

relievervelo

Obviously, there are a lot more relievers than starters, but the data is basically the same. As you can see, the slope of the regression line is very similar – there doesn’t appear to be a significant difference between starting and relieving in terms of correlation between fastball velocity and strikeout rate. The r (not squared, which I’ve adjusted based on a couple good comments this afternoon) is .43 for starters and .38 for relievers.

Of course, this is for major league players only. How does velocity interact with strikeout rate in the minors? We’ll look at that tomorrow.

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Dave is the Managing Editor of FanGraphs.

12 Comments
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Matt Harms
16 years ago

It’s interesting that while the slope of the trend lines are nearly identical, their starting points are different. Granted, it isn’t *that* much of a difference, but it reinforces the notion that relievers many times are just failed starters. IE, the starters can get about 0.5 more K/9 for a given fastball speed than the relievers can do at the same speed.

Very cool, great analysis Dave.

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fili
16 years ago
Reply to  Matt Harms

I would like to see the slope presented. I’m not sure they are that similar. The trendline for starters starts above 4 and ends up below 8. The trendline for relievers starts below 4 and ends up well above 8, maybe above 9.

Also, noted the cloud distribution with the relievers, breaking them down farther would be helpful. There are some pretty extreme outliers there (11Ks/85MPH for example)

Agreed that K/BF would be more helpful

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fili
16 years ago
Reply to  Matt Harms

Just noticed that both the X and Y scales for both graphs are inconsistent. That’s bad presentation form :0)

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