Baseball Prospectus’ resident injury guru Will Carroll offered up his take on Joba Chamberlain’s injury:
The early word is that his muscle tightened up due to a combination of the blistering heat (I sat in that heat the night before, and yeah, it’s a huge factor) and fatigue. It’s the latter that’s most worrisome given Chamberlain’s switch of roles. While he built up his arm strength, no one has any idea how the fatigue will be affected by the shape of his season. He’s headed back to New York for tests, so we’ll know more soon, but early reports and sources tell me that things look relatively positive, based both on the pain’s location, and on his reaction. Expect the Yanks to be ultra-conservative, and for Chamberlain to miss a start at least. We’ll know more after the images, but I’ll leave the DXL as a TBD for now.
Carroll’s report is pretty much the best-case scenario for Joba. He could be going through a dead-arm period, but Carroll doesn’t note which muscle tightened up. Some reports have Joba’s deltoid as the muscle in question while others are relatively vague.
Again, we don’t really know anything beyond what Joba, Joe Girardi and a few unnamed sources have said. Strength tests were positive last night, but any time there’s fatigue or stiffness around the throwing arm, there is cause for concern. Hopefully, we’ll know more later.