McAvoy was forced to leave after taking a slapshot to the face from Canadiens blueliner Noah Dobson with just less than nine minutes remaining in the middle frame.
The 27-year-old went down to the ice immediately and was helped to the locker room by the Bruins’ training staff.
Before exiting, the American D-man had logged 13:41 of ice time, blocked three shots and taken a slashing penalty.
Entering Saturday’s game, McAvoy has recorded 14 assists while averaging 24:20 minutes of ice time over 18 contests.
