Mitchell, who is averaging 28.4 points in his first season for Cleveland, got hurt Monday in the third quarter of a 113-103 win over New Orleans. He was held out of practice Tuesday, and the Cavaliers ruled him out hours before tipoff against the streaking Grizzlies, who have won 10 straight.
With Mitchell on the bench, the Cavs rallied to beat the Pelicans. Darius Garland scored 30 points for Cleveland, which overcame a 13-point deficit.
It's not yet known if Mitchell will miss multiple games. The Cavs are always cautious with injuries and Mitchell is their best player and an MVP candidate.
Mitchell has helped get the Cavaliers back among the Eastern Conference's top teams since arriving in an offseason trade from Utah. Earlier this month, he scored 71 points in an overtime win against Chicago.
The Associated Press contributed to this report.