Matt Swartz at Baseball Prospectus broaches the topic of Ol’ King Cole Hamels, creepy ad man. Swartz thinks Cole is A-OK.
[…] the difference between 2008 and 2009 is abnormally good luck in the first and abnormally bad luck in the second. The first clue was that he had similar peripheral statistics in 2008 and 2009. He struck out 21 percent of hitters in both years, and walked just over five percent of hitters in 2009 after walking just under six percent of them in 2008. His ground-ball rate stayed roughly the same, rising from 41 to 43 percent. The difference came from his [Batting Average with Balls in Play] BABIP jumping from an incredibly fortunate .262 to an incredibly unfortunate .321. It has been shown many times before that BABIP is a statistic with low persistence, and that pitchers see their performances jump up and down constantly with respect to this statistic. As a result, much of year-to-year fluctuation in ERA is tied to fluctuations in BABIP. Unsurprisingly, Hamels ERA went from 3.09 in 2008 to 4.32 in 2009. As Hamels’ peripherals indicate an ERA around 3.65, it seems likely that he had a mixture of good luck in 2008 and bad luck in 2009 that belied his ERA.