Sunday, January 11, 2009

Pitchers and Luck Pt. 2

Following up on yesterday's post, I wanted to offer this brief analysis, which more precisely measures the degree to which luck factored into each Nationals pitcher's success (or lack thereof) in 2008. The goal here is to calculate exactly how many runs per 9 innings the pitcher allowed (or prevented) because of bad (or good) luck. The method is to simply take tRA* minus RA, and this gives us a precise "RA luck factor."

If you're not used to dealing with RA, it's just the same as ERA, except with the unearned runs left in. Since there's a strong case to be made that the distinction between an unearned run and and earned run is pretty arbitrary, RA is in some ways a better point of comparison. Again, the difference between ERA and RA is usually about .40 runs, so you can make that quick conversion in your head if you like.

Here are the results.

RA tRA* Luck
Mike Hinckley 0.66 4.44 3.78
Steven Shell 2.52 4.43 1.91
Scott Olsen 4.73 5.29 0.56
John Lannan 4.40 4.74 0.34
Daniel Cabrera 5.45 5.78 0.33
Joel Hanrahan 4.27 4.06 -0.21
Garrett Mock 4.39 4.12 -0.27
Saul Rivera 4.39 4.09 -0.3
Collin Balester 5.96 5.10 -0.86
Jason Bergmann 6.06 4.61 -1.45
Shairon Martis 6.10 4.45 -1.65
Shawn Hill 6.68 4.98 -1.7
Marco Estrada 9.24 4.57 -4.67

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