The Canadiens have announced goaltender Carey Price is sidelined with a concussion until his symptoms reside.
The head injury comes after Price was struck in the face mask by a shot in Tuesday's game against Philadelphia.
Price appeared shaken up by the shot but played for the rest of the game.
The news came as 32-year-old defenseman Shea Weber will undergo surgery after tearing a tendon in his foot.
Weber is believed to have been injured when hit by a shot in the opening game of the regular season.
Coach Claude Julien said this week that Weber played through the pain until he had to come out of the lineup.
He skated in 20 of the first 21 games, took six games off, then played six more before going on the injured list for good.
It is the second time in the last three seasons the Canadiens have lost a star player for the season. In 2015-16, it was Price with a knee injury.
In both cases, the player was expected back within weeks of the injury, only to see his absence drag on until he was finally shut down for the season.
The team said surgery will be required because the injury didn't heal as expected.
"After further exams, and a consultation on Wednesday in Green Bay, Wisconsin with specialist Dr. Robert Anderson, and with Shea's approval, it has been determined that he should undergo surgery and will be out for the reminder of the season," team orthopedic surgeon Paul Martineau said in a statement.
"Our medical group will work with Shea to ensure he is pursuing the best course of treatment moving forward, and we expect him to make a full recovery and be ready for the start of training camp next season. The length of his recovery will be determined following surgery, which will be performed by Dr. Anderson."
The Canadiens have struggled with their top defenceman either hampered by injury early in the season or out of the lineup since December.
As when Price was injured two seasons ago, they are unlikely to make to the playoffs.
-With files from the Canadian Press