Stevens said the team does not have an immediate timeline for Irving's return. Guard Marcus Smart will start in Irving's place against the Sixers.
"He's been evaluated by our docs and everything else," Stevens said. "Don't feel like it's a long-term issue, but he is sore and has been, and so hopefully he can get to feeling better sooner rather than later."
Stevens added that the team's medical staff has thoroughly evaluated Irving's shoulder.
"I think that he was getting treatment on it, and I don't know if it got aggravated after last game," Stevens said. "But after the last game, he noted it more. And then [the medical staff] spent a lot of time with him in the 24 hours following."
Based on fan balloting, Irving was positioned to be named an All-Star starter on Thursday night. Through 43 appearances this season, Irving was averaging 24.1 points, 5.0 assists, and 3.6 rebounds over 32.7 minutes per game.
Entering Thursday's games, the Celtics have the best record in the Eastern Conference at 34-11 -- three games ahead of the Toronto Raptors and seven in front of the Cleveland Cavaliers, Irving's former team.Celtics'Irvingsoreshoulder,Sixers