Makar was hurt early in the third period on Saturday after taking a hit from the Bruins' Brad Marchand. He remained on the ice until Colorado was able to gain possession before heading to the locker room; he did not return.
Makar leads all rookies and ranks tied for second among NHL defensemen in scoring with 28 points (eight goals, 20 assists) in 29 games. He was named the league's Rookie of the Month for November after producing 16 points (seven goals, nine assists), the most by a rookie defenseman in any month since Alexei Zhitnik registered 19 in March 1993 with the Los Angeles Kings.
"He finds a way to contribute every night, and most of that is getting us in and out of our zone, using his skating ability to do that, as well as in transition to be a part of it and getting us playing on the right half of the ice," Bednar said of Makar. "That is a big minus out of our lineup with him out tonight for sure and maybe for the next couple games."
Grubauer was injured after making a save late in the first period of Colorado's 4-1 win at Boston and left the ice at the ensuing whistle, which came from Valeri Nichushkin scoring to tie the game at 1-1 with 2:45 left before the intermission. The Avs keeper was able to finish the contest on the bench as the backup.
Grubauer had won his previous three starts and has recorded a 1.82 goals-against average and .935 save percentage in his past four games.
Colorado enters the matchup against the Flames with 90 man-games lost to injury or illness. Fifteen Avs players have already missed time this year.
"We're still a good team with guys out, but we're a much better team with everybody healthy obviously," said Nathan MacKinnon, who has stepped up offensively during this period with 45 points on the season. "It's great to have Mikko (Rantanen, who missed 16 games earlier with a lower-body injury) and Gabe back. We still got guys in and out right now, but to have those two guys is a huge help."
In addition to Grubauer, Kadri and Makar, Erik Johnson is out with a lower-body injury he suffered from being pushed headfirst into the boards by Alexander Kerfoot on Nov. 23 against the Toronto Maple Leafs--a play that resulted in a two-game suspension--and Colin Wilson is set to have surgery to help fix a lower-body issue after getting hurt during practice on Oct. 29.
Calvert missed Saturday's contest in Boston while on a person leave of absence, but it wasn't related to the head injury that forced him to miss six games from Nov. 19-30. He will play tonight when the Avs wrap up their season series versus the Flames.
To make room for Calvert and Werner, the Avalanche reassigned forward T.J. Tynan to the AHL's Eagles after morning skate.