The Duncan Effect

At Inside Pulse Sports Pip of Fungoes asks:

it’s time for a comprehensive study of whether there is a “Duncan Effect” on pitchers, like the one that JC Bradbury did on Leo Mazzone. Until then, no one knows for certain what kind of an impact (if any) Duncan has on pitchers.

Well, because you ask so nicely, I’d be happy to oblige. 🙂 Actually, it’s easy because I already did the study.

Two years ago, Sports Illustrated asked me to look into the question, and I ran a study similar to the one I did for Leo Mazzone in The Baseball Economist. I looked at how pitchers performed with and without Duncan, controlling for factors such as age, parks, and pitcher quality. I found that Dave Duncan’s pitchers improved their ERAs by about 0.35 runs—yeah, he’s pretty darn good.

If you haven’t seen this before, it’s because the estimate buried on page 60 of the September 27, 2007 issue of SI in a story about Duncan and his sons. I meant to write about it at the time, but I never got around to it.

UPDATE: Pitchers Hit Eighth posts the link to the SI article in the comments. Thanks!

4 Responses “The Duncan Effect”

  1. SMS_Mike says:

    That’s fantastic. We all thought Duncan was an elite pitching coach, and it’s nice to see some statistical analysis to back that up.

    I don’t think I still have that issue of SI laying around. Any way you can post a pdf of the article here?

  2. Thanks for the info, JC.

    So it’s quantifiable that all of the talk about Duncan reviving careers and improving everyone else’s castoffs is actually true (at least in the instances where the individual pitcher actually improves). 🙂

    FWIW, here’s the SI article:


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