Having read Sheng's article about it being a hip injury for Celebrini, and then watching the play again several times where he crashed into the boards (hip first) in the preseason, I'm pretty confident that he's just dealing with a hip pointer.
This would, in a way, be ideal, because a hip pointer is painful but should heal up in a few weeks, and I imagine it would only lead to other problems if he's playing and overcompensating. It's kind of incredible just how quick and nimble he looked on Thursday considering this.