Ben Simmons played nearly 30 minutes in the All-Star Game Sunday, scoring 17 points on 8-of-9 shooting for Team LeBron.
Thursday night he is out for the 76ers as they return to action.
Simmons' status for Saturday's showdown against the Bucks will be announced Friday, the team said.
Simmons is averaging 16.9 points, 8.3 assists, and 7.9 rebounds a game for the Sixers this season as the starting point guard. He's also been playing All-Defensive Team level defense.
Simmons was suffering lower back tightness on Wednesday, told the Sixers medical staff and got treatment, but it was back Thursday morning. After more treatment, the decision was made to have him sit, reports Paul Hudrick at NBC Sports Philadelphia.
This will be just the third game Simmons misses this season, building off the 79 games he played in last season.
Simmons isn't the only All-Star out upon his return, Kemba Walker is out for Boston on Friday night.
Walker was a starter for Team Giannis on Sunday and played nearly 30 minutes, scoring 23 points on 18 shots.