Joba’s injury has been described as more of a back problem, but it is technically an oblique strain. He’ll be shutdown for a few days, but isn’t expected to miss much time.
This doesn’t seem to be as serious as Mitre’s injury, but the two pitchers play different roles so this could effect them in different ways. Mitre is trying for a rotation spot and will likely be the long-man if he doesn’t win that job. Compare that to Joba, who is a lower level middle reliever who will likely pitch just one inning at a time, and Mitre’s injury effects him more. Joba just won’t need the same amount of innings as Mitre meaning that shutting him down effects him less.
Either way, this doesn’t seem like a big deal right now. It’ll only become a problem if it lingers, but Joba could be shutdown for two full weeks and still have enough time to get ready for the season.