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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.

                              Year 1                                                                 Year 2

Starter Type

Injury Rate

Days on DL

Starter Type

Injury Rate

Days on DL













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.



K Rate


BB Rate








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
Crow projects to have by far the worst strikeout rate (7.5 batters per nine innings) in the rotation of any of these arms, and he’s also the most susceptible to the long ball. While that K rate would still be a slightly above-average figure, it wouldn’t make him a potential top-of-the-rotation option. As a starter, Crow struggled with his mechanics in the minors, putting up a five-plus ERA with a strikeout rate reminiscent of PECOTA’s projection. He faded in the second half of last season, recording a small-sample 7.36 ERA in August and September, and he suffered from a stiff shoulder and forearm tightness after the All-Star break despite throwing only 62 innings all season. That doesn’t bode well for his ability to handle a heavier workload. He also allowed a lofty .323 TAv to opposite-handed hitters last season, so he could be vulnerable to teams stacking their lineups with lefties.

4. Aroldis Chapman, Reds
For Chapman, the rotation outlook is mixed: he has both the best projected strikeout rate (10.9 per nine) and the worst projected walk rate (5.0 per nine) of the five starting candidates. The most walk-prone qualifying starters last season, James McDonald and Gio Gonzalez, walked only 4.1 per nine. If Chapman issues free passes much more often than that, he’ll be hard-pressed to remain in the rotation despite all the strikeouts. He does have the most fearsome fastball of this hard-throwing bunch, but he has yet to demonstrate that he possesses a reliable third pitch beyond his heater and slider, and the spectacular difficulty he sometimes experiences in repeating his delivery—as he did last April and May, when he walked 20 batters in 13 innings and required a remedial trip to the minors—doesn’t bode well for his ability to go deep into games.

3. Neftali Feliz, Rangers
Feliz’s secondary stuff has stagnated during his extended stay in the bullpen, and in the rotation, his blistering fastball can’t quite carry him like it did in relief. He also saw some significant decline in his peripherals last season, striking out batters at only a league-average rate for relievers and walking too many batters, to boot. If those rates don’t rebound, he could struggle to remain an effective closer, let alone a budding ace. However, the Rangers have gone through this process before with Wilson and Ogando, so Feliz could benefit from any lessons the team learned the last two times.

2. Daniel Bard, Red Sox
Bard completely fell apart in his last season as a starter, walking 78 batters in 75 innings in class-A and High-A in 2007. Given that his last experience with starting bordered on Steve Blass disease, the risk in removing him from the relief role in which he did find success is obvious. After his starting struggles, the Red Sox allowed him to abandon the mechanical changes they had forced him to adopt early in his pro career and revert to the delivery that had made him a first-round draft pick in 2006. While that seemed to bring an end to his troubles, he did fight through some mechanical struggles last September, walking nine and pitching to a 10.64 ERA in 11 innings (tiny sample alert). However, his fastball could sit at 95 as a starter, and he has an effective slider and changeup that will serve him well as he attempts to go deep into games.

1. Chris Sale, White Sox
Sale has the second-highest projected strikeout rate (10.7 per nine, just a tick below Chapman’s) and the lowest projected walk rate (3.4 per nine) of the talented quintet. His development of a new slider grip last season gave him an effective third pitch to pair with his mid-90s heat and plus changeup, and he’s also showed the smallest platoon split of any of these pitchers, which means that he won’t suffer much from increased exposure to righties. However, look hard enough at any of these pitchers, and you can find red flags. Sale is the only one who hasn’t started as a professional, and his skinny 6’6” frame could prove too fragile for the strain of starting.

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 Insider.

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I watched Bard's start over the weekend on MLB .... He got two outs right away and then walkd a batter 4 straight ... he righted the ship and had an easy 2nd inning.
He sat at 93-95 occasionally touching 97. By taking a little off his slider it has a significant break and his 89 mph dipping change up is an out pitch to right handed hitters.

In an interview he talked about how sore his arm got as a reliever last year .... with 70 something appearances and another 30 where he warmed up and did not go into the game.

I could see him have a similar path as Ogando did last year where he finds a groove May June July and then hits a wall....but not many starting pitchers in Baseball have his stuff.... if the command is there - huge upside.

Sale will benefit from tutelage under the slightly built Jake peave who learned from Greg Maddox in San Diego to "ease" your way into the game first time through the order ...I sat behind Home Plate at Petco once excited to see Peavy and was incredulous as he got through the 1st four innings against the Dodgers with moving fastballs ranging from 89-92 ....then innings 5-8 hit 95 and 96 when he had to make a pitch ... Hells Bells finished off the 4-1 victory for the Pads.

The only positive I can correlate with Feliz - who seems to be somewhat lazy - is that he gets to work with Mike Maddoz to restore his secondary offerings.

Regarding Bard, how unusual is it for a reliever to not come in 30% of the time he warms up? Sounds high to me, but has anyone monitored that? I'd think teams would be hesitant to give that info out.
Given the cautions for Crow, and given the improvements they have made in their bullpen, do you think that the Royals might be inclined to make Crow a 5-inning starter this season?
Perhaps, I missed it, but the most obvious attribute a reliever would have that corresponds to success in a conversion to starter would be the number of effective pitches he can throw, no? Was that tested for correlation to conversion success or is that too difficult to define?
Couple of follow-ups ...

Re: Bard's interview ... he talked about all the times he was warming in the pen and the Red Sox either blew or more often extended a lead. ThWhae times a starter wriggled off the hook or the times when a loogy was needed to get the last out(s). While his "30" might have been his estimation, it is a reality of the relief pitching game that they warm up and then dont pitch. Taking it a step further - as a former pitcher I can tell you that the urgent and intense manner that a relief pitcher warms is not condusive to arm health.

Re: Crow - I think the move is one of desperation by the Royals ...for a starting pitcher. They have a plthora of power arms in the bullpen and can afford to toss him to te wolves out of desperation.

As Hoot comments - as a starting pitcher you need to have three pitches that you can command as a minimum in order to get through the lineup three times ....

Most starting pitchers will add and subtract to their fastball and even their slider at times.

One key attribute is to have the ability to "GRIND" ... you have to be a grinder as you might have your good stuff only 60-75% of the time you "go to the tit" ... Grinders are winners - they compete no matter what ... 35 starts over 6 months - to excel over that entire length of time makes one a special starter.
Quick thought: If you can predict something better than PECOTA by adding a simple dummy variable (converted reliever = 1), why isn't it added to PECOTA?
And a related thought: how do you value low-inning players going into a draft? It seems to me like a pitcher that averages 7 innings but is held back for the last month to stop from surpassing 160 IP might be valued more highly than someone who consistently throws 5 innings and reaches 160 IP (and puts up otherwise identical stats), because you can slot some other pitcher in once the converted reliever has been benched. On the other hand, if you have a playoff system, the opposite might be true. Has anyone looked at this?