I was in the middle of the final 2010 Sleepers, Comebacks and Busts article, which will cover the closers, when I came across the name Andrew Bailey and noticed that he had thrown over 80 innings last season (83.1 to be exact). Which brought to mind something I had read before (on espn.com I think?) about how relievers who throw 80-plus innings tend to fall off the next season. Heath Bell comes to mind from 2007 to 2008. Bell threw 93.2 innings in 2007 and his 2008 numbers regressed quite a bit in ERA and WHIP especially. I wanted to do some research for myself to see how this could possibly affect a pitcher like Andrew Bailey in 2010, going back to 2007 and using 80 innings pitched as the cut-off point.
2007 to 2008
It seems like there is a noticeable correlation between high innings totals and a fall or or injury the following season. Interestingly, it doesn't seem to be the strikeouts that are affected as much as command. Most pitchers on this list saw a rise in walk rate the following year. While there are some exceptions, the vast majority ran into this issue. The good thing is that most pitchers who made it through 2008 healthy and decreased their innings bounced back in 2009.
In 2008, for the first time in a long time, no reliever surpassed 90 innings, though J.P. Howell only missed by point two innings. The most interesting name on this list is Carlos Marmol. Not only did he throw 87.1 innings in 2008, but he also prepared for the World Baseball Classic prior to the 2009 season as well. The good thing is that Marmol only threw 1.2 innings in the WBC, so that shouldn't affect his overall total much, if at all. That means we could see a nice correction in Marmol's command to go along with his top-end strikeout potential, making him a great value on draft day.
2009 relief pitcher innings leaders
Baliey is the only one on this list that has a closing job on opening day 2010. Something that may help him is the fact the he was a starter in the minors, but generally it doesn't seem like pitchers find a lot of success making such transitions when they throw a ton of innings as a reliever. It is a completely different routine and training program, including recovery time in between outings. This information gives me some reservations on just how well Bailey can perform in 2010, especially coming off of a season in which his BABIP against was extremely low (.234) and his strand rate was quite high (85 percent).