Karlsson left after a tough tackle in the second period when he injured his arm or wrist.
"It was, of course, very tough to lose him. Everyone knows how good he's been and how important he is to us," said teammate and defender Rasmus Andersson to Aftonbladet.
Coach John Tortorella does not believe Karlsson can play any more in the final series.
"He's an important part of our team, but he probably won't be with us. We have to fill that void, not just with one player, but as a team," Tortorella said after the game.
The match ended 4–2 to Carolina, who now lead 3–2 in the series and can decide the final series on Monday night local time in Sweden.
