SAN JOSE — Joe Thornton and Logan Couture are the new poster-childs of hockey toughness.

Thornton played in four Stanley Cup playoff games last spring with ACL and MCL tears in his left knee. Couture suited up for the Sharks entire series against the Edmonton Oilers even though his mouth was being held together by wires and plastic, the result of taking a puck to the mouth just two-and-a-half weeks earlier, which made it excruciatingly painful just to eat, talk and breathe.

But Thornton and Couture both insisted Friday that there is one injury that they wouldn’t be willing to play through: a concussion.

“That’s where you draw the line,” Thornton said. Like our Sharks Facebook page for more San Jose Sharks news, commentary and conversation.

The risks of playing with concussions grabbed the attention of the hockey world this week when former-Anaheim Ducks star Paul Kariya, who will be inducted into the Hockey Hall of Fame in November, opened up about his experiences with head injuries in an interview with TSN’s Micheal Farber.

Long before Thornton and Couture earned their tough-guy points, Kariya, 42, was immortalized for his heroics in the face of injury during the 2003 Stanley Cup Final.

After taking a blindside headshot from New Jersey Devils defenseman Scott Stevens in Game 6, and spending 48 seconds lying motionless on the ice with a concussion, Kariya returned to the ice, scoring a key goal that helped the Ducks stave off elimination.

Kariya’s goal is one of those indelible moments that will pass the test of time for hockey fans, similar to Carleton Fisk’s home run in Game 6 of the 1975 World Series in baseball.

But Kariya, who suffered six documented concussions in his career, has no memory of the goal or the rest of Game 6. He doesn’t remember playing in Game 7 either.

“I saw the Paul Kariya thing, too. That’s a different animal than a broken bone or a ligament,” Sharks coach Pete DeBoer said. “(Concussions) are so individual. They’re scary.” For complete Sharks coverage

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Over the course of his 20-year career, Thornton has witnessed the evolution of concussion research and the changing attitude toward head injuries in professional sports. Back in the 1990s, if a player suffered a concussion, they called it getting your bell rung. You shook it off and returned to the ice as soon as possible.

“Now, you have spotters during the game, there’s a protocol that you have to go through with the training staff,” Thornton said.

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The incident came after Crosby missed Game 4 of the series in the wake of a concussion he suffered in Game 3. Like Kariya, Crosby has been plagued by concussion issues throughout his career. He missed half of the 2010-11 season and all but 22 games in 2011-12 to recover from a head injury.

After Crosby smacked his head on the boards in Game 6 last May, head coach Mike Sullivan told reporters that he did not undergo testing with the team’s training staff. Crosby contradicted his coach a day later, saying that he was examined by a team doctor during the first intermission and was cleared to play.

The incident raised questions about whether the concussion protocol needs to be taken out of a team’s hands and handled by independent doctors.

If a player as competitive as Crosby, Thornton or Couture wants to return to the ice with a concussion, can the team doctors really stop him?

“With the doctors we have here (with the Sharks), if it’s as bad as he (Kariya) had it, no one would be playing,” Couture said. “I’m certain of that.

“I’m a guy that’s had head injuries before, I know the consequences down the line. It’s up to the player, as well, to realize that you’ve only got one brain and that injury is very, very serious.”

Thornton agreed.

“They (the team doctors) wouldn’t want you to go back on the ice,” he said. “That’s something that we’re glad and thankful for. With the protocol now, they just say, no, you’re not going back out until you pass these tests.

“It’s protection from yourself.”

Both Couture and Thornton said that the attitude toward head injuries in the locker room has shifted dramatically over the last few years as players have become more aware of the long term impacts.

“You definitely want to take your time, especially with all the science we have behind concussions now,” Thornton said. “You want to make sure you’re better because that’s your brain. You can come back from a groin or a knee, but your brain, that never heals.

“When you’re 40, and you can’t remember stuff, that’s scary.”

Contrary to popular belief, DeBoer insists that the NHL is doing a good job of educating its players about the long-term risks associated with concussions. He’s confident that the protocol would stop his players from returning to the ice like Kariya did 14 years ago.

“Opening training camp meeting, we had a concussion video from the league presented to the players,” the Sharks coach said. “That’s the first thing they’re hearing after the opening remarks, pretty much. They’re very educated on it and we’re all trying to learn as much about it as we can.”