San Jose Sharks forward Joe Thornton had arthroscopic surgery Thursday to repair an injury to the medial collateral ligament in his right knee.
There is no timetable for his return, the Sharks said.
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Thornton was injured when teammate Mikkel Boedker fell on him with less than one minute remaining in the third period of a 5-4 overtime loss to the Winnipeg Jets on Tuesday.
The Sharks recalled forward Marcus Sorensen from the San Jose Barracuda of the American Hockey League and placed Thornton on injured reserve Wednesday.
Video: NHL Tonight crew talks about Joe Thornton's injury
"Next man up, business as usual," Sharks coach Peter DeBoer said after a 6-5 loss against the New York Rangers at SAP Center on Thursday. "It's a fact of life in the NHL. … There's not much you can say. I think our group has to be next guy up and let's figure out a way to fill the void and get the job done.
"I don't know the long-term prognosis. I know he's not going to be available in the near future. … I'm concerned with coming out of the break and going into Pittsburgh (on Tuesday)."
Thornton, 38, has 36 points (13 goals, 23 assists) in 47 games this season. He had surgery on the MCL and anterior cruciate ligament in his left knee during the offseason.
That injury was sustained April 2, 2017, and caused Thornton to miss the first two games of the Western Conference First Round against the Edmonton Oilers.
Thornton returned to the lineup for Games 3 through 6, and the Sharks lost in six games.
"You never know when a guy hurts himself like 'Jumbo' did when he's coming back," Sharks forward Logan Couture said of Thornton. As much as it hurts to play a game without the big guy, you've got to step up and other guys have got to run with the opportunity. … It's a good time to make an impression right now."
Thornton, in his 20th NHL season, is 16th in scoring with 1,427 points in 1,493 games with the Sharks and Boston Bruins. He's 12th with 1,030 assists, three behind Mario Lemieux for 11th.
He is playing on a one-year, $8 million contract he signed July 2.
"The guy's a legend," Sharks defenseman Brent Burns said. "It's tough to lose a guy like that. Say whatever (you want), but other guys get a chance for a bigger role, more ice. Teams lose top guys all the time. You've got to battle through."