Boston Celtics guard Marcus Smart is out indefinitely after reportedly suffering a torn tendon in his right thumb, according to Shams Charania of Yahoo Sports. 

Smart will get a second opinion on the extent of the injury. 

The 24-year-old is averaging 10.2 points, 3.5 rebounds and 4.8 assists over 54 games, including 11 starts, this season, his fourth with the Celtics. 

The Celtics hold a 46-21 record and are 3.5 games behind the Toronto Raptors for first place in the Eastern Conference.