PITTSBURGH — Next week, Chris Kunitz will celebrate his 37th birthday.

At that age, most hockey players have already started thinking about how much longer they can keep playing what is becoming an increasingly young man’s game. Kunitz, though, only has to look across the Penguins’ locker room at 39-year-old Matt Cullen for a reminder that he may still have a few years left in the game.

As he prepares for his 13th NHL training camp, Kunitz, entering the final year of his contract with the Penguins, isn’t worrying too much about what the future has in store.

“If you come to the rink happy and enjoying what you’re doing, I don’t think it’s time to change that,” Kunitz said after an informal workout last week at the UPMC Lemieux Sports Complex.

“You look at some of the veteran guys that are around the league, the Cullens and the (Jaromir) Jagrs, some bodies hold up longer and better than others. As long as you go out there and contribute to your team — I think that’s the main indicator —that you’re still having fun, still enjoying what you’re doing.”

If last season is any indication, Kunitz still has plenty to contribute.

Like most of his teammates, last year started slowly for him, with just 13 points in his first 40 games. As the team heated up, though, so did Kunitz. He found some consistency playing alongside Sidney Crosby and Patric Hornqvist and saw his production increase as well. He had 27 points in his last 40 games of the season and added four goals and eight assists during the Penguins’ Stanley Cup run.

The biggest takeaway for Kunitz, though — especially as one of the team’s elder statesmen — was how fresh the team was even after a grueling 24-game playoff run.

“One of the things I came away with in the playoffs was that our team was probably ready to play another game if we had to,” Kunitz said. “We weren’t exhausted, we weren’t mentally broken down. I think on that note, we were just ready for that next game. ‘Bring it, let’s go, play.’ That’s kind of how it is now.”

By “now,” Kunitz means heading into training camp, where the first objective will be to wipe last year’s playoff run from their collective memories. Kunitz has been on two defending championship teams in his career — the 2008 Ducks and the 2010 Penguins — and neither of those teams advanced past the second round of the playoffs.

“People come to talk to you, call you the defending champs,” Kunitz said.

“You have to go out there and honestly prove it every day. You have to go out and earn your space again.”

The Penguins return virtually every key player (except defenseman Ben Lovejoy) from last year’s Cup run, but Kunitz cautioned that doesn’t necessarily guarantee success.

“You have to work twice as hard to get back into the rhythm,” he said.