BP Unfiltered: Aceves Crosses Enemy Lines

Nothing gets the competitive fuels flowing like a player moving from a team to its hated rival. Alfredo Aceves may not spark the fire like Johnny Damon or even Ramiro Mendoza by jumping from New York to Boston, but he is worth discussing because the Red Sox envision a role change. The Yankees had Aceves make five starts over three big-league seasons, but mostly used him in long relief. The transition does not appear to be as outlandish as it may sound.

Aceves’ top PECOTA comparisons are Leo Rosales, Tony Pena, and David Wells—yes, that David Wells. While many recall Wells as a starter for roughly half of all major league teams over the course of a long career, he broke into the big leagues as a reliever. Wells did not make more than 25 starts in a season until he turned 27. Aceves just turned 28 and the pair share roughly the same peripherals.

Having numbers similar in nature to a successful convert and having the right stuff to make the transition are two different topics. PitchF/X data suggests that Aceves throws a four-seam fastball, a cutter, a changeup, and a curveball, with the secondary offerings receiving nearly equal usage (between 15-20 percent). Many relievers are on the outside looking in at the rotation because they lack the weaponry required to defeat opposite-handed batters. The variety in Aceves’ offerings is evident in his career stats. In a nearly equal number of plate appearances, Aceves has held righties to a 663 OPS and lefties to a 603 OPS.  

Aceves’ career ERA as a starter is 3.42 (in five starts), while his career reliever ERA is 3.16 (in 54 appearances). The sample size for starts is so small that little is gained from evaluating the numbers. Instead, a decent projection can be formed by using Aceves’ relief numbers and employing a reverse application of the Rule of 17 – where Aceves’ ERA goes up one run per nine innings pitched, his strikeout per plate appearances goes down 17 percent, his batting average on balls in play goes up .017 points, and his home runs per contacted plate appearance goes up 17 percent.  The results look like this:

Those numbers come close to Dallas Braden’s 2010 season (he struck out 14.5 percent, walked 5.5 percent, and had a .273 batting average on balls in play) which seems like an optimistic comparison for Aceves. After all, the last time he made a season’s worth of starts came in 2008 when he did so across the upper minors and to fair results (a 2.62 ERA and 4.22 strikeout-to-walk ratio). Aceves’ injury issues also put his performance expectations into question.

Because Boston is stacked with starting pitching options, Aceves will likely find himself either in the Pawtucket rotation or the Boston bullpen. He could make a spot start or two over the length of a season, but there should be no aspirations of becoming a regular anytime soon.