if they're concerned that the surgery won't be as successful since it's his second go-round on the Tommy John procedure.  If that's the case, trying to rehab it first makes some sense, since it could give him two shots are recovering and continuing his career.  There have been guys who have had the surgery more than once (Jose Rijo, Victor Zambrano, Chad Fox, and a few others), but I can't think of anyone that came back after a second TJ surgery and performed at anything approaching their prior level, with the possible exception of Al Reyes.  

Andrews himself put the success rate (i.e., a pitcher returning to the his previous performance level) of second Tommy John procedures at just 20% in a USA Today article last year.  "You can always get it redone, but it won't be as good as the first time."

Looking at it from Capuano's perspective, where the priority isn't this season or even next, but the rest of his career, if there's a chance that rehabbing it will work, why not try that first?  If it doesn't work, he can still get the TJ procedure done later and hope for the best.