From what I've read, its the abdominal muscle that is strained, and that injury is very annoying in that there's no real treatment for it and you just have to be very patient with it. Its the kind of injury that hurts when you cough/sneeze and such, so you can't completely rest it like other muscle strains. I'd rather have him just wait for it to heal and come back completely healthy. Hopefully that is sooner rather than later, though.
Too bad my backup SS is Yuniesky Betancourt.