Boston Bruins defenceman Charlie McAvoy will be out at least four weeks with a sprained MCL, the team announced Tuesday.

McAvoy was injured in the first period of Saturday’s contest against the Montreal Canadiens following a Brendan Gallagher hit.

Boston says McAvoy’s injury will be re-evaluated in four weeks.

The 20-year-old has 32 points in 59 games, including seven goals and 25 assists. He averages 22:06 of ice time a game, second on the Bruins to Zdeno Chara.

“We’ll be without Charlie for a little bit, but we’ve got lots of depth and he will be back,” head coach Bruce Cassidy said. “Hopefully he heals quick and keeps his conditioning up.”

The Bruins are also without forward Patrice Bergeron, who will be re-evaluated next week after a foot fracture sustained on February 24. Goalie Tuukka Rask is out with a lower body injury and won’t play Tuesday against Detroit.

McAvoy is a critical piece of Boston’s defence, but he’s been out this season before. He missed four games around the All-Star break to repair an abnormal heart rhythm. The Bruins were 3-1-0 in that time frame and made a few adjustments, shifting Brandon Carlo to his pairing with Chara.

As Cassidy notes, the Bruins do have considerable depth and won’t have much trouble filling the pairs.

Matt Grzelyck will skate with Kevan Miller, while Nick Holden will be paired with Torey Krug. Adam McQuaid is expected to be scratched against the Red Wings thanks to the play of Grzelyck.

Krug and Holden will likely see extra time on the power play in McAvoy’s absence.

As of press time, the Bruins are 40-15-8 with 88 points. That’s three points ahead of the Toronto Maple Leafs and six points behind the league-leading Tampa Bay Lightning.