The MRI results on Joba Chamberlain's left side showed an "injured oblique," and he's out indefinitely. He suffered the injury during Friday's appearance, and the Yankees initially thought he would be well enough to pitch sometime in the middle of this week - that's certainly not going to happen. Not that I can really trust YES's radar gun, but he hit 97 mph during Friday's appearance and was down to 89 by the end of the inning. His curve and slider were also significantly slower than they had been. Again, I don't know if this had anything to do with the injury; it could've just been the gun being weird.
The Yankees don't seem too concerned, but oblique injuries can be nasty. Still, if Chamberlain had to miss a portion of the regular season, the bullpen would be just fine, considering Rafael Soriano and David Robertson are around for setup work.