Wheeler, 33, is kind of the opposite of Bobby Jenks. While Jenks pitched well last year but had poor results thanks to bad luck and bad defense, Wheeler has spent the last few years enjoying tiny BABIPs--likely due in part to his high fly ball rate--and the deceptively low ERAs that come from them.
Still, Wheeler is a solid fourth option out of the pen, given he should only really be pitching in sixth and occasionally the seventh inning, and hopefully against righties, against who he's consistently recorded low xFIPs. Wheeler is prone to the home run when facing lefties, however, which is pretty much the last thing you want out of a reliever.
Though this would seem to complete the Red Sox' bullpen, they might not be content with having Felix Doubront acting as a lefty specialist instead of a Triple-A starter, and so could be looking to add one more southpaw before the year is over. Combining a LOOGY with Wheeler as the ROOGY would essentially give the Sox 4 reliable innings of production with Atchison and Wakefield still available for long relief duties.
Wheeler will receive $3 million in 2011, with a $3 million team option in 2012 that vests with 65 appearances, per Alex Speier.