Decades ago, bullpens didn't have defined roles. A reliever was just someone who came in to finish things up when the starter couldn't go the distance. Even as the idea of a closer emerged, relievers still soaked up multiple innings at a time -- it's how Hall of Fame closer Rollie Fingers threw over 1,200 innings between 1972 and 1982, all while making just a pair of starts. Mariano Rivera, the most likely of present-day relievers to enter Cooperstown, just crossed the 1,200-inning threshold for his career. It took him 17 seasons to do what Fingers achieved in a decade, because Rivera threw over 100 innings in a season just once.
Closers like Fingers don't exist at all in today's game, and relievers like him are few and far between. There have been 13 pitcher seasons since 2001 with a minimum of 100 innings pitched and 90 percent of appearances coming out of the bullpen. Just three of those have occurred in the last five years.
Specialization of roles has a lot to do with why these kinds of seasons from relievers continue to dwindle, but is there any reason that this role can't be reinvented? Think about it: relievers are considered overrated given they don't throw enough innings. There are pitchers who aren't good enough to be starters, but by the same token, it's something of a waste to use them for 50-70 innings a year if they have the ability to do more than that. Giving them more innings to throw would once again change the landscape of bullpens, create more valuable relievers than what we are used to seeing, and possibly open up one more bench spot for a position player.
In today's game, with so much information available, advantages are fewer and farther between: more efficient use of roster spaces is one way to keep ahead of the curve, and a super reliever can help with that.
It's not as simple as preparing a pitcher to throw more innings, though. And that's probably at least part of why seasons like Alfredo Aceves' 2011 are so rare these days. Aceves came to camp with the Red Sox prepared to start, but ended up moving to the bullpen for most of the year. He made four spot starts, accounting for 21 innings pitched, but the bulk of his 55 appearances came out of the pen, totaling 93 innings.
Those 114 innings had value, too. According to Baseball Reference's wins above replacement (rWAR), Aceves was one of the 10 most valuable relievers in baseball in 2011. He didn't have the pure numbers of closers Rivera or Craig Kimbrel, but he made up for the difference in quality with quantity: combined, Kimbrel and Rivera threw just 24 more frames than Aceves. The difference in rWAR would have been even less had Aceves stuck in the pen all year, where he is a better fit, rather than throw 21 forgettable innings in the rotation.
From a scouting perspective, relievers capable of ~100 innings have to possess sound mechanics; staying consistent not only helps with command and effectiveness, but helps prevent injury. Because of the workload and frequency of appearance, they also have to have pace in their arsenal, meaning they can't be max effort, grip it and rip it types. To establish pace, it helps to have a starter's arsenal; that way speeds can be changed and sight-lines altered to keep the hitters off-balance.
But unlike starters, super relievers need to have ready arms that are quick to warm and can take 30-plus pitches three-to-four times a week. Starters have a very specific routine, with appearances every fifth day, tailored sessions in between, workouts, stretching, etc..
Relievers, specifically relievers with heavy workloads, need to act as a starter but prepare like a reliever. Not every pitcher can prepare as a reliever: quick to warm, maintaining arm strength, avoiding fatigue, etc.
Aceves has a deep arsenal, and he's not one to beat hitters with speed. Rather, he throws quality strikes, and tends to keep hitters off balance by controlling the count. He prepared as a starter for 2011, but spent the year in relief: being stretched out to throw more allowed him to do just that relative to your standard reliever.
Aceves isn't the only reliever with more than two pitches who isn't quite talented enough to start. Why is he the only one who had this role in 2011? Teams have just moved away from this model, but there are reasons to believe it should return. Someone like Aceves, who can throw multiple innings more than once per week, can help to shoulder some of the starter's workload. That will be useful for the Red Sox this year as they attempt to convert Daniel Bard to a starter, much like Aceves was helpful in 2011 when Tim Wakefield couldn't always get through six innings.
The Rangers could attempt to use Alexi Ogando like this, assuming Yu Darvish signs and slots into their now overloaded rotation. Ogando might not have the stamina to throw 200 innings, but quality-wise, he is good enough to start, and has prepared and succeeded in relief before. With Neftali Feliz moving to the rotation, Ogando might be useful in the same way Aceves could be for Bard. If the Rays can't find the proper trade partner in their six-man rotation, figuring out which of Wade Davis or Jeff Niemann might have the arm and approach to a successful super reliever stint could be worth exploring. Even if they do move a starter, they are loaded with nearly MLB-ready pitching prospects, and one of them might qualify for the role. The Yankees have pitchers like Joba Chamberlain, Phil Hughes, and Hector Noesi, a group that might yield exactly zero major league starters, or three -- one might be a better fit as a 100-inning bullpen anchor. The Blue Jays already have someone who has done this before, in Carlos Villanueva.
Not every reliever can do this, but not every reliever needs to. Baseball people like to copy things that succeed, though, so if other teams can find the same success with some of their own arms that Boston did with Aceves last year, then the idea of the super reliever could catch on. Again.