The play occurred just under four minutes into the third period as the rookie phenom went to retrieve the puck behind his net.
Makar has already established himself as one of the league's elite blue-liners with a sensational rookie campaign to date. The 21-year-old entered Saturday's action leading all first-year players - and tied for second among NHL defensemen - with 28 points in 29 contests.
Avalanche goaltender Philipp Grubauer also left the contest in the first period and did not return.
Head coach Jared Bednar did not provide an update on either Makar or Grubauer following the game, according to The Athletic's Ryan Clark.
The Avalanche won the game 4-1 to hand Boston its first regulation loss at home this season.