While many members of the Braves' bullpen wore down as the season progressed, Peter Moylan did exactly the opposite, struggling early and finding his stride late in the year. Much of that improvement likely has to do with distancing himself further from his Tommy John surgery last season, and once he got going, he was valuable indeed. Moylan had surgery on May 8, 2008, and after he was 13 months--a typical full recovery period out from the procedure, batters hit just .234/.306/.310 against him and he posted a 1.75 ERA after June 8. Even including the portion of the season where he was presumably still getting his strength back, his GB/FB ratio rose to 3.20, as if his 2.48 mark in 2007 wasn't impressive enough. His fastball velocity was down a couple MPH from its pre-surgery levels, but we don't have data to say whether that improved over the course of the season. The fact that his slider velocity was actually better suggests that his slower fastball isn't necessarily a side effect of surgery.
Moylan isn't a conventional closer; he's not going to come in and blow away hitters like Rafael Soriano often did in 2009. That said, Moylan is plenty effective, and he even has the added advantage of versatility: he can come in to bail his 'pen mates out of an eighth-inning jam and then finish the game, whereas many closers struggle when they don't get to enter the game with a clean slate. He can also throw multiple innings if Bobby Cox can bring himself to let Moylan pick up a two-inning save. Should Rafael Soriano and/or Mike Gonzalez walk this winter, Moylan could get an extended look in a closing role.
Of course, making Moylan the closer removes a very valuable middle-inning option, someone that can come in and get a double-play grounder in a tight spot or give you two innings in the event of a short start. Ideally, the Braves would bring in a more traditional fireman for the ninth inning, and continue to let Moylan be the bullpen's durable utilityman.
The bottom line: Moylan's strikeout and save totals might not be eye-popping next year, but he could become the 'pen's most valuable reliever given a full season at 100% strength.