I think it was in the All-Star thread. Hopefully it's nothing. But you could also view it as good news, i.e. a tangible minor physical issue that explains his recent struggles versus regression, the league catching up to him or him running out of steam. I could also truly be just a one-time occurrence.
Or the worse case, that it has flared up due to him compensating for something else that hasn't been recognized.
Right now their position is still that he makes his next start. But they're still going to use Phillips (along with Nola and Sanchez) before either he or Wheeler go again. Beyond that, they'd be stuck filling another gap or rushing Walker back.