After breaking into the Ducks' zone with the puck, Max Pacioretty reversed the puck up the boards, and with the puck long gone, was hit from behind by Clayton Stoner. Pacioretty had trouble getting to his feet after the hit, and needed help from the Canadiens' trainers to leave the ice. On his way down the tunnel, it was apparent that Pacioretty couldn't straighten his back.
The Canadiens announced that Pacioretty would not return to the game, which is horrible news for the Habs going forward. Pacioretty is easily the most important forward on the Habs, and losing him for a long period would take an already poor possession team to among the league's worst.