That's not good, but at least he doesn't need surgery. The Post-Gazette reports that he's been diagnosed with "significantly restricted range of motion" in his shoulder. I'm not a doctor, but that sounds like more of a symptom than a cause to me. Let's hope there's nothing else to it and that he'll be ready to go in a month, but it sounds to me like another shoe is going to drop here.
The same article reports that Jimmy Barthmaier and his ailing elbow will miss a month with a strained flexor mass.