Boston Celtics guard Marcus Smart grabs for his left leg after being injured against the Los Angeles Lakers.

An MRI on Boston Celtics guard Marcus Smart revealed a “Grade I tear” in his left calf and he is expected to miss 2-3 weeks, according to an injury update from the team.

Smart underwent the MRI on Sunday morning to determine the severity of the injury he suffered late in Saturday’s 96-95 loss to the Los Angeles Lakers.

The Celtics played the final 10:28 without Smart, who was helped off the court with what the team said was a left calf strain following a collision with Lakers forward Montrezl Harrell underneath the basket. Harrell tipped in a missed layup and stepped on Smart’s foot as he came down.

Smart crumpled to the court. He was helped to his feet but couldn’t put any pressure on his leg as trainers carried him to the locker room. The Lakers surged following the injury, with LeBron James putting the Lakers ahead on a 3-pointer with 5:25 to play.

Smart’s injury was the latest blow to a Boston lineup that was playing with its projected starting lineup of Smart, Kemba Walker, Jayson Tatum, Jaylen Brown and Daniel Theis for just the second time this season.

Walker missed the first 12 games of the season recovering from a procedure on his left knee and Tatum missed multiple games earlier this month with COVID-19.

— The Associated Press contributed to this report.