Irving said he has battled increasing soreness in his shoulder in recent weeks and is sitting out Thursday's game as a precaution. Irving said he could be back on the floor for Sunday's game against the Magic.
Marcus Smart starts in Irving's place Thursday against the Sixers.
"Just precautionary stuff and just making sure everything is all right from a strength perspective," Irving said before Thursday's game. "Obviously a few days will definitely put me where I need to be, and we'll just see what goes on for Sunday's game. It's nothing too crazy. It was just giving me a little discomfort over the past few weeks, and I've just been playing through it, in terms of preparing best for every single game, and I just felt it best to get a few tests and make sure everything's all right."
Irving described the soreness as "gradual" but said it affected his shot and driving to his left. He expressed heightened concern to Boston's medical staff after Tuesday's loss to the New Orleans Pelicans and underwent imaging that confirmed no structural damage.
"I did it for precautionary reasons and everything was fine," Irving said. "So, structurally, everything is good in my shoulder, and I'm [going to] do what's best, take a few days to strengthen it up even more and then try to give it a go Sunday."
Irving said he wants to be able to play without worrying about the shoulder.
"I'm just really fortunate to be somewhat ambidextrous out there, and when I'm out there trying to drive left and the ball isn't bouncing the way I would like it to or feel as comfortable as I would like, then that was a cause for concern on my end," Irving said. "I didn't really need to say anything. As much as my pain tolerance is, I wasn't really worried. The last game, when I was shooting in pregame, was probably the most discomfort I've felt. I obviously played throughout the game, but afterward I knew I had to kind of get an MRI just to make sure everything is cool."
Celtics coach Brad Stevens said team doctors were confident Irving's injury wasn't a long-term concern after the testing.
"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."
Also before Thursday's game, Irving was named to the Eastern Conference All-Star starter pool, finishing as the top vote-getter among East guards. Through 43 appearances this season, Irving was averaging 24.1 points, 5.0 assists and 3.6 rebounds over 32.7 minutes per game.
"I am truly appreciative of the fans of the NBA and the Boston Celtics for voting me in to this year's All-Star Game as a starter," Irving said. "I am super proud that I can represent the Celtics in L.A. and looking forward to putting on a show."
Entering Thursday's games, the Celtics owned 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.