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Saturday, May 25, 2013

Reliever Pitching Metric Correlations, Year-to-Year | FanGraphs Baseball

It makes perfect sense. Starters having more pitches to fall back on. Relievers usually only have one or two good pitches, so the pitcher has less options to make adjustments.

This lines up well with what Jeff Zimmerman and I found regarding pitcher aging and how it differs depending on a pitchers role.

Let’s take the example of strike outs. Jeff and I found that while starting pitchers were able to mitigate against their decline in velocity–and therefore experienced a less drastic decline in their strike out rate–relievers were far more dependent on their velocity. As a result, relievers generally were more likely to see sharper declines in strike out rates from year to year.

Jim Furtado Posted: May 25, 2013 at 10:28 AM | 2 comment(s) Login to Bookmark
  Tags: pitching, sabermetrics

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   1. valuearbitrageur Posted: May 25, 2013 at 01:24 PM (#4452001)
Finally an explanation for the rapid decline of Mariano Rivera.

Only 6.x K/9, and has given up almost 4 runs in barely 18 innings
   2. Mike Emeigh Posted: May 25, 2013 at 02:00 PM (#4452022)
If you read the comments, MGL makes an important point:

Without matching up the underlying number of TBF (so that it is the same for starters and relievers), a comparison of correlations is worthless.

As it turns out, if you use the same number of underlying TBF (which is difficult obviously, since relievers max out at around 300 or so), you will find that relievers have a HIGHER correlation than starters. My guess is that their true talent changes less from season to season for a variety of reasons, perhaps one of them being more stable health due to fewer pitches thrown.


Relievers face about 1/3 the number of hitters that starters face, so you would expect more Y-T-Y variability simply because of the smaller samples.

-- MWE

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