A Red Sox closer hasn't missed time with a significant injury since September of 2006. The rest of the roster has seen its share of injuries, many of which helped derail playoff aspirations, but, excepting the shoulder subluxation that caused him to miss one month, that closer spot has been locked down with the durability of Jonathan Papelbon for the last six years.
Andrew Bailey hasn't even pitched in a regular season game for the Red Sox yet, and now there's a possibility he will not only miss the first week or two due to a thumb injury, but could be out even longer as he recovers from thumb surgery.
Without knowing what's wrong, or how much time he will be out, it's hard to gauge just how much of a problem this is for the Red Sox. But either way, we can look at what the Red Sox bullpen will look like without its expected closer in it to start the year. In past years, the bullpen was shallow, but had the highly-effective Papelbon as well as Daniel Bard in it. Last year's iteration was much deeper, but depth only takes you so far when your starting pitchers are throwing the fewest innings of anyone else in the majors: the workload caught up, and Boston's pen no longer seemed as strong as it was.
The projected 2012 bullpen, even without Bailey, still features a deep collection of talented arms. It would be better with Bailey, of course, as he's an excellent closer when he's actually on the mound: he has a career 2.07 ERA with a 3.6 K/BB, and that isn't all thanks to his former, pitcher-friendly home park in Oakland. But, unlike in say, 2009 or 2010, an injury to the closer doesn't automatically spell doom for the Red Sox bullpen. There are more than two arms here with mentioning for a change and not in the, "Well maybe Hideki Okajma will be good again" kind of way.
Closer and Setup Candidates: Mark Melancon is a former closer, acquired by the Red Sox from the Astros this past off-season in exchange for Kyle Weiland and Jed Lowrie. He misses plenty of bats, whiffing just under eight per nine for his career, and also induces grounder after grounder when opponents do make contact. Were Bailey not around, he would likely have been Boston's closer, and has the stuff to thrive in that role.
Alfredo Aceves didn't win a spot in the rotation, in part due to his versatility. His strengths are his own downfall, as he's proven himself ready to pitch whenever and wherever the Red Sox need him. With Bailey out, the "wherever" might be the ninth inning. If Bailey is out in the short-term, Aceves might even be capable of closing out both the eighth and ninth, as he has the arm to throw well over what a normal closer would. He doesn't strike out many hitters, but Aceves pounds the strike zone and induces weak contact, helping him rack up innings efficiently. If it ends up being Melancon as the temporary closer, Aceves is capable of handling the seventh or eighth, and very well might have even if there were no injury to Bailey.
Big picture, Vicente Padilla is a candidate to be an average-ish starter. He's thrown 200 innings just once since 2004, though, and it's likely he's better-suited for relief at this stage. The 34-year-old Padilla has plenty of velocity on his heater, and like Aceves, a wide array of pitches he can use to mix things up. Padilla is easily the least-productive of this trio, but a closer's job is, relatively speaking, simpler than that of a setup man. If Padilla were to start the ninth, regardless of whether he's up by one, two, or three runs, he gets to come in with a clean slate: no baserunners, and a need for just three outs. The setup pitchers have it tougher, with fewer fresh innings, and more appearances where runners are already on (and likely in scoring position), and the chance of having to go more than just the one frame. Having the better relievers in those tougher spots make sense, especially since Padilla is certainly capable of getting three outs before he gives up a couple of runs.
There's also the chance, if Bailey isn't out for very long as surgery is deemed unnecessary, that the Red Sox don't name a specific closer, and instead just use these three to get them through the late innings in whatever order they are available in that day. It's more high-leverage-by-committee than closer-by-committee, but it's an option.
Middle Relief: This area has been a weakness in the past for the Red Sox. Typically, Boston had Papelbon and then Okajima, or Papelbon and Bard, and then had a difficult time finding a reliable third option, never mind reliable middle relief arms.
There are a few intriguing relief arms for 2012, though, even with the Bailey injury. Franklin Morales is free from Coors Field, and doesn't need to build on his 2011 to be productive for the Red Sox. Matt Albers was real good for the Red Sox last year until his command left him at the wrong time, but is working on bringing back old pitches of his to combat that problem. Scott Atchison should never be in the high-leverage frames he was forced to work out of necessity in 2010, but he throws strikes, and can do some good if relief innings need to be eaten to give everyone else a rest.
The real intrigue of the middle relief corps comes from what we'll dub The Projects. Rich Hill is recovering from Tommy John surgery after a short (but dominating) stint as Boston's go-to lefty. He'll be back in 2012, and if he's the Rich Hill we know he can be, then he could be their top left-handed reliever. It's Hill, though, so there are no assumptions being made: he's labeled a project for a reason. The same goes for Andrew Miller, who is likely starting the year on the disabled list with a strained hamstring. Pitching coach Bob McClure is getting his chance to fix Miller by keeping him from throwing across his body, attempting to get Miller's wicked stuff to finally translate into production in the majors. It's something that's been tried many a time before, though, so he's not something they can rely on just yet. Michael Bowden transformed into a fastball/cutter/slider pitcher, like so many other Red Sox arms, and while he's found success at Triple-A, it hasn't happened in the majors just yet. Non-roster invite Justin Thomas threw 10 innings this spring, likely due to the injuries that slowed the pre-season's of his fellow lefties -- he's a possibility to join the Red Sox early on.
Daisuke Matsuzaka and Aaron Cook will likely start rather than reliever, but if Daniel Bard and Felix Doubront are working out in the rotation, then they will need to pitch somewhere, assuming they have worked back to health or haven't opted-out, respectively. (If one or both of that pair isn't working out in the rotation, then guess who will be on bullpen duty instead of Dice-K or Cook?) Alex Wilson, who was in the initial running for a rotation job this spring, could be called up from Pawtucket as a reliever should they require another arm with some upside to throw some innings.
It's misleading to say that there's no shortage of arms, or to assume that every one of these players is going to work out for the best, but even with Bailey injured, the Red Sox likely have enough relievers to keep things moving along without a major problem. The further they get into the year, the more options they will have, too, thanks to pitchers like Hill and Wilson. It would be a better bullpen with the expected closer, but for once, the loss of the stopper in Boston isn't necessarily a death knell for the late innings.