It wasn’t the absolute worst of news for Charlie McAvoy and the Bruins, but things are still looking a bit grim.

Hours before their Tuesday night tilt with the Red Wings, the Bruins announced that McAvoy suffered a sprained MCL just 37 seconds into the team’s 2-1 win over the Canadiens Saturday night at TD Garden. The rookie blue-liner will be re-evaluated in four weeks.

“Charlie sustained a sprain of his left MCL and will be re-evaluated in four weeks,” general manager Don Sweeney said in a team statement. “The injury occurred on March 3 in the first period of the Bruins game against the Montreal Canadiens at TD Garden.”

The Bruins have some big shoes to fill on the back end without McAvoy, who leads all rookie defensemen with 32 points (7 goals, 25 assists) in 58 games. Brandon Carlo will partner with Zdeno Chara on the top defensive pair, while Nick Holden will slot with Torey Krug on the second pair and Matt Grzlecyk will make his return after missing the last two games with a lower-body injury and pair with Kevan Miller.

The four-week timeframe presumably means McAvoy will be re-evaluated between late March and early April.

Tuesday’s game with the Red Wings begins the Bruins’ season-ending stretch of 19 games in 34 days.