Tired of being pigeonholed as a reliever, Aaron Heilman has demanded a trade from the Mets, as he wants them to find a team that will give him a shot to return to his roots as a starting pitcher. Other teams have found success moving relievers back into the rotation, Ryan Dempster being the most recent success, and Heilman was a first round pick as a starter in 2001, so there will probably be a team out there that believes that he’s worth a shot as a starter.
How successful will the conversion be? First off, let’s try to determine how good of a reliever Heilman has been.
Over the last four years, Heilman has tossed 357 innings, walked 131 batters, struck out 322, and allowed 29 HR, which adds up to a 3.67 FIP. That’s solidly above average for a reliever, but doesn’t make him a true relief ace. However, he wasn’t consistently above average all four years.
From 2005 to 2007, he ran a K/BB rate of between 2.61 and 3.15, showing good enough command of his fastball/change-up combination to throw strikes while missing a decent amount of bats. He sustained a pretty low HR/FB rate, which helped him keep the ball in the yard even though he’s not a dominant groundball pitcher. His FIP for those three years was 3.34, and he was a very good setup man.
Last year, however, his walk rate went through the moon, jumping from 2.09 to 5.45, and his HR/FB rate spiked, causing him to be a bit home run prone. It could be random variation, where he just had a rough year finding the strike zone, but a quick look at his pitch selection reveals an interesting change – Heilman started throwing a lot more sliders last year, throwing them in 12% of his pitches versus just 0.4% a year prior. The change-up dropped from 37.9% to just 24%, as the slider made him more of a three pitch guy and less dependent on the change.
The slider may have helped him miss a lot more bats, but he got those gains in strikeout rate by throwing way too many pitches out of the strike zone, and the end result was a jump in walk rate that was more detrimental than the jump in strikeout rate. If the rise in use of the slider was the cause the of dramatic jump in both BB and K rates, it appears to have been too detrimental to be worth it.
It will take a full breakdown of Pitch F/x data for us to determine whether the slider was the cause of the command problems, but it seems likely that the rise of the slider usage wasn’t a coincidence.
What does this mean for Heilman as a starter? Well, there aren’t that many successful starters who rely on strictly a fastball/change-up to get by. Almost every starting pitcher has some kind of breaking ball that they can use to change the plane of a hitters eye, and if Heilman just can’t command his slider, that could be a real issue in moving him into the rotation.
As a fastball/change-up guy, he was a very good reliever. As a fastball/change-up/slider guy, he was something of a mess. It’s not enough to conclude that he doesn’t have a chance as a starter, but I’d call this a buyer beware situation.