Last year Philadelphia Phillies pitcher Cole Hamels had his worst season as a starter. Many baseball analysts cited the Verducci Effect for his drop-off in performance however the effect was also there in 2008 yet Hamels had one of his best seasons.
What is the Verducci Effect? Named for the Sports Illustrated baseball writer Tom Verducci, who discovered it, the Verducci Effect is a "negative forward indicator for pitcher workload"1. The requirements for it are a pitcher under the age of 25 and who has pitched more than 30 innings over the previous season. In the subsequent season the pitcher will under-perform.
Last season Cole Hamels met the requirements of the Verducci Effect and underperformed as predicted. In 2008 Hamels was 25 years old and pitched 72 more innings than he did the previous season. In 2008 Hamels had one of his best seasons going 14-10 with an ERA of 3.09. Furthermore he was named the Most Valuable Player (MVP) of both the National League Championship Series and the World Series.
However in 2009 Cole Hamels had his worst season as a pitcher just as the Verducci Effect would predict. Those 72 additional innings in 2008, including 35 in the post-season, seemed to have taken their toll on Cole. In 2009 Hamels was just 10-11 as a starter with an ERA of 4.32. Additionally he was not the dominate pitcher in the play-offs that he was in 2008.
So it is simple then, the Verducci Effect explains Cole Hamels in 2009. Not so fast, the same Verducci Effect predicted a drop-off for Hamels in 2008 and it is not clear that he under-performed that year.
In 2007 Cole Hamels threw 58 innings more than he did in 2006. In 2007 Hamels had a good season going 15-5 with an ERA of 3.39. Now by the Verducci Effect 2008 should have been a bad season for Hamels but it was not, Cole was 14-10 and the World Series MVP. Remember the Rule of 30 (30 more innings than the previous season), Hamels pitched almost twice that number of innings (58) yet did not have a big drop-off in his stats.
Many seam-heads now take the Verducci Effect as almost baseball gospel but Cole Hamels makes me question its validity. Is the Verducci Effect statistically valid? Maybe Hamels is just an outlier? Whatever the case may be, the effect no longer applies to Cole. He is now over 25 years old.
1 Baseeball Prospectus glossary.