BOSTON — This guy plays a hazardous, vulnerable position in a violent, contact sport, gets more playing time than any teammate, is routinely matched against opponents’ best players – and he’s 40 years old?

He’s not Tom Brady, but the Bruins are certainly impressed by the Patriots’ seemingly ageless quarterback. The Bruins, however, are kind of partial to their own age-defying 40-year-old, captain Zdeno Chara.

“It’s crazy,” winger Matt Beleskey said. “I don’t know how he does what he does at 40. I’m 29, and feel like I feel now – I can’t imagine if I kept playing ’til 40.”

“When you see him, see his size, his work ethic, all these things, you can’t help but to be a little bit amazed,” said Adam McQuaid, one of many Bruins defensemen Chara has mentored. “And there’s still a respect factor in here: ‘Wow, that’s Zdeno Chara.'”

Chara embarks on his 20th NHL season in Thursday’s 2017-18 opener against the Predators at TD Garden. Include nearly 150 career playoff contests, and he has played almost 1,500 NHL games. This will be his 12th season with the Bruins (922 games, including 102 in the postseason), all of them as captain.

All of them, as well, as the no-question, go-to, No. 1 option when the Bruins need a defensive stop – something not likely to change this season, either.

“Until he proves he can’t play, he’s our guy,” Coach Bruce Cassidy said. “He’s our shut-down guy. And I don’t see that happening any time soon, personally.”

While his days as a relied-on producer (seven seasons of 40 points or more in Boston, three with at least 50) have dwindled as others have filled his power play role, Chara’s defensive game remains elite: His plus-18 rating tied winger Brad Marchand for the team lead last season, he averaged a full minute more than the next teammate in shorthanded time on ice (3:46) for the NHL’s best penalty-killing unit, and he did all that while playing with rookies – Brandon Carlo during the regular season, Charlie McAvoy when Carlo got hurt just before the playoffs.

So how does he do this?

The legendary size – 6-foot-9, 250 pounds – helps, as do a strict diet and fanatical training habits. The bloodlines aren’t bad, either: His dad wrestled for Czechoslovakia in the 1976 Olympics, a year before Chara was born.

“I think he took, like, three weeks off the ice this summer – no, not even that – and then he was back working,” Beleskey said. “You watch the way he takes care of himself, what he does off the ice. The proof is in the pudding with him.”

Chara doesn’t deny how much he loves training.

“I always try to come to camp as ready for the season as I can,” he said. “My goal is not just to complete the testing – I want to be the best. I want to be winning the competitions, winning the races.”

Chara isn’t content to just stay big and strong, though. He wants to stay current, too. Knowing that big, punishing teams like the 2010-11 Bruins he captained to the Stanley Cup have been overtaken by younger, faster crowds, Chara is determined to keep pace.

“He’s a big man, but he works so hard on his skating, on his skills, to keep up and keep doing what he does,” Beleskey said. “You watch him out there in a skills session, he’s dialed right in, ready to go. He loves that stuff.”

“He’s a student of the game,” McQuaid said. “When there are changes in the game, he’s able to evolve, which is something I really admire.”

Chara appreciates such admiration and respect, and is hopeful it manifests itself in more time with the Bruins. He’s in the last season of a seven-year, $45.5 million contract (this year’s salary cap hit is $4 million), and has told the Bruins he wants to play past this season – preferably in Boston. General manager Don Sweeney hasn’t ruled it out; Chara’s happy about that.

“There aren’t many athletes, in general, in their 40s, who are still at a high level of performance,” he said. “I’m proud of what I’ve been able to do, how I still feel.”