"I think the hard part -- at the end of the day -- to swallow is that he's been shut down for an extended period of time," said Philadelphia coach Peter Laviolette, who learned the news just before the game. "Where there was hope, right now there's not."
Flyers general manager Paul Holmgren made the announcement through a team spokesman early in the first period. Most of the players learned the news from reporters after the game.
"Obviously, that's devastating, to say the least," Scott Hartnell said. "He's a presence. That's the best thing I can say about him. He's a presence in the room, he's a presence on the ice, and he was a big factor in our run a couple of years ago. And when he's in the lineup he really brings a lot of intangibles a lot of guys can't bring, so obviously we're upset about it and I'll give him a call when we get out of here."
Sergei Bobrovsky stopped 28 shots for Philadelphia, which blew 1-0, 2-1 and 3-2 leads in the second period.
"We're a resilient bunch and when we dig ourselves holes like that we know what we have to do to get back in games," said Simmonds, who scored for a fourth straight game 18:10 into the second. "We have a never-say-die attitude and we're never going to give up, ever."
Philadelphia has won nine of 10 and is first overall in the Eastern Conference with 43 points, two ahead of Boston and a point behind Minnesota for the overall NHL lead.
Erik Cole scored the Canadiens' third tying goal of the period with 15.5 seconds.
Louis Leblanc got his first NHL goal and David Desharnais also scored earlier in the second for Montreal, which lost in regulation for the first time in seven games (3-1-3).
"We had to be better," Canadiens coach Jacques Martin said. "We were up against the best team in the East and they capitalized on our mistakes."
In addition to learning they had lost Pronger for the rest of the season, the Flyers also are without star forward Claude Giroux, the NHL scoring leader with 39 points. He missed his second game in a row and is out indefinitely with a concussion after taking an inadvertent knee to the head from Simmonds on Saturday.
Carle got his third point when Meszaros gave Philadelphia its fourth one-goal lead with a slap shot past Price from the point.
The Canadiens evened it for the third time in the second moments after Simmonds made it 3-2 with his ninth goal, his fifth in six games.
Cole got credit for his team-leading 12th goal on a puck that struck him in front of the net and bounced over Bobrovski and came to rest on its edge just over the goal line inside the right post.
Desharnais erased the Flyers' first one-goal lead 5:02 into the second with a strong individual effort. The Canadiens center held the puck patiently as he carried it out from behind the net, moving his way to the slot to fire a shot past Bobrovksi to tie it at 1.
Zolnierczyk made it 2-1 with his second goal of the season at 5:48.
Leblanc, a Montreal native who was the Canadiens' first-round pick in 2009, drew a huge ovation for his first goal in eight games at 13:24.
Talbot scored his ninth goal 12:07 into the first.
Pronger last played since Nov. 19. ... Canadiens LW Travis Moen missed the game with a lower-body injury sustained Tuesday night in a victory over the New York Islanders.
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MONTREAL, CANADA - DECEMBER 15: Harry Zolnierczyk #29 of the Philadelphia Flyers passes the puck in front of...