March 12, 2012
The Once and Future Starters
Five talented young pitchers are attempting to enter the rotation this spring after making their first marks in the majors in relief. Neftali Feliz, Daniel Bard, Chris Sale, Aroldis Chapman, and Aaron Crow have all excelled in the bullpen, but they don’t have a single big-league start between them. However, they do have starting experience: all but Sale, who started in college, have pitched out of the rotation in the minor leagues, and Chapman was also a starter in Cuba before signing with the Reds in 2010. Are their teams making the right move by returning them to their original roles, or will they regret messing with their young arms’ early success?
Most relief pitchers begin their baseball lives as starters before being banished to the bullpen. Relatively few pitchers ever succeed in the rotation after becoming established as relievers. If all five of this spring’s newly-minted starters—who range in age from 22 (Sale) to 26 (Bard)—stick in the rotation, their simultaneous success would be unprecedented. Since 1950, there have been six seasons in which four pitchers successfully converted—throwing at least 100 innings predominantly as starters a year after throwing at least 50 innings predominantly in relief—but five would be a first. No pitchers pulled off the feat last season. Alexi Ogando came close to qualifying (he threw only 41.2 innings the year before), and Phil Coke tried and failed, but the last two to do it were C.J. Wilson and R.A. Dickey, both in 2010.
If Feliz, Bard, Sale, Chapman, and Crow have bid their final farewells to the bullpen, sabermetricians will celebrate. It’s not hard to see why: statistics suggest that starters are the most essential members of the pitching staff. Last season, 70 pitchers made 30 or more starts in the majors. They averaged 2.1 Wins Above Replacement Player (WARP). The best reliever in baseball, Craig Kimbrel, earned 2.2 WARP. If an average starter can add as much value as an elite reliever, it’s in every team’s best interest to extend as many of its arms as possible.
Even when we look exclusively at pitchers who appeared in both roles, we see the same value advantage for the starters. From 1987-2011, pitchers who were primarily relievers in one season and primarily starters the next saw their WARP roughly triple after entering the rotation. As starters, their ERAs rose, their strikeout rates fell, and—since they were no longer limited to pitching late in games—their innings came in lower-leverage situations. Yet because they threw more than three times as many of those innings, they provided far more value to their teams.
Of course, most pitchers who make 30 starts in a season are at least moderately healthy and effective, so if Feliz, Bard, Sale, Chapman, and Crow reach that threshold in 2012, their teams will probably be pleased. (The few who managed to make that many starts in 2011 without pitching well, like Brad Penny, the groundball artist formerly known as Fausto Carmona, and A.J. Burnett, were banished to Japan, jail, or worse—Pittsburgh—this winter.) But as the numbers in the preceding paragraphs suggest, they don’t have to be aces to make their conversions worthwhile.
Is there any evidence that might contradict the conventional conclusion that teams should seek out starters whenever possible? One of the factors most often cited as a reason not to remove a reliever from the bullpen, despite what the stats say, is the risk of injury. Intuitively, it would seem that asking a pitcher to increase his workload dramatically would place a greater strain on his arm, leading to more frequent and more serious injuries. According to BP’s injury database, though, that isn’t the case.
From 2002-2011, the years for which we have complete injury information, converted starters in their first exposure to the rotation actually hit the DL less often and spent less time on the sidelines than other starters. In their second season in the rotation, they got hurt at roughly the same rate and with similar severity.
There are a couple reasons why this could be true. Converted starters may have less mileage on their arms; once they’ve been in the rotation for a full season, they face more wear and tear, which could explain why their injury advantage evaporates in their second year as starters. Alternatively, teams may monitor converted starters’ workloads more carefully. The Rangers will reportedly cap Feliz at 140-160 innings this season, and both Red Sox pitching coach Bob McLure and White Sox pitching coach Don Cooper have expressed their intention to keep a close eye on Bard and Sale, respectively.
It makes sense to give all five of these arms a shot at more innings, but there are statistical indicators that suggest some of them are better-suited to starting than others. For the most part, the qualities that serve pitchers well in short outings—missing bats, avoiding walks, getting ground balls—also serve them well as starters. But by comparing PECOTA’s baseline projections for 90 converted starters since 1950 to their actual results, we can see whether any traits were associated with greater success than expected.
Two of these factors—strikeout rate and walk rate—are weakly but significantly correlated with a comparative advantage in the rotation, above and beyond the advantages that high strikeout rates and low walk rates always provide (which are already reflected in the baseline projections). With that in mind, how can we rank these aspiring starters in order of likely success, from least to most likely? (Note: don't take these rankings too seriously—these guys are all pretty good.)
5. Aaron Crow, Royals
4. Aroldis Chapman, Reds
3. Neftali Feliz, Rangers
2. Daniel Bard, Red Sox
1. Chris Sale, White Sox
Despite those legitimate causes for concern, it’s clear that the potential payoff for all five of these teams justifies the risk in removing their young pitchers from a role in which they’ve already succeeded. Not every pitcher who dominates in short bursts can make a smooth transition to starting. Any statistic that purports to prove how much more valuable relievers can be in the rotation suffers from significant selection bias, since the only relievers who make that move are the ones deemed capable of doing so. However, Feliz, Bard, Sale, Chapman, and Crow have all received that seal of approval from their organizations this spring, and no one knows their capabilities better than the teams that drafted, signed, and developed them.
Many of the decisions that have to be made when deciding whether to stretch out a pitcher come down to scouting. Does his stuff play up in the pen? Does he have enough effective pitches to fool hitters a third time through the order? Does he have the mechanics and mental and physical makeup to handle grueling games interspersed with long layoffs between outings? The numbers available to outside observers can’t answer all of those questions. But the numbers we do have tell us that these five teams are making the right move by trying to squeeze more innings out of their existing arms.
Thanks to Colin Wyers for research assistance.
A version of this story originally appeared on ESPN Insider .