The NESN documentary “Chara at 1,000’’ — a tribute to Zdeno Chara, the Bruins’ fierce 43-year-old defenseman — is an informative and often charming look behind his curtain of stoicism, further revealing a person who is an authentic leader on and off the ice.

Named after the games-played milestone he achieved in January, the doc debuts Sunday at 7 p.m. on NESN. It’s an hour well spent.

Jack Edwards, who has called the vast majority of Chara’s 1,023 regular-season games with the Bruins over the past 14 season, narrates and conducts the interviews on the franchise pillar.

But it was during an interview about the doc earlier this week that Edwards drilled to the core of why Chara, who has been the Bruins captain since arriving as one of the great free-agent signings in NHL history in 2006, is so respected by present and former teammates.

“Athletes respond to deeds and actions,’’ said Edwards. “You can say all the right things and do all the right things off the ice. But the way you function as a team leader is to do the most difficult thing at the most difficult time. That leaves your fellow teammates saying, ‘Wow, I don’t know if I could have done that.’ There are thousands of those moments in Zdeno Chara’s career.’’

In the documentary, former teammate Marco Sturm puts it more concisely when he talks about how Chara’s relentless attitude changed the Bruins in his early years.

“Go as hard as you can,’’ says Sturm with a smile, “because if you’re not, the big guy gets mad.’’

Having set foot, or skate, in the Bruins locker room is not a requirement to comprehend what Chara means to the Bruins. In the doc, he describes his leadership style like this: “I’m not afraid of a challenge. I’m willing to lead by hard work, dedication, discipline, drive.’’

This is not news to Bruins fans, who have the fresh memory of the man playing with his broken jaw wired shut in last year’s Stanley Cup Final. Or, in a more welcome memory, remembering that he saluted his teammates with a downright giddy double-finger-point before receiving the Stanley Cup from commissioner Gary Bettman after the Bruins won Game 7 of the 2011 Final.

It’s not news that the Bruins are a habitually united team in large part because Chara — who banned hazing of younger players because he felt it detrimental to the cause — always put the team first, even above his own well-being.

But the documentary does provide — or at least revive — plenty of news in its chronology of his life and career, particularly regarding how far he has come in his journey from a regimented childhood in Slovakia to becoming a third-round pick of the Islanders (Mike Milbury famously drafted him off a grainy VHS tape) to an uncertain future once he arrived to play junior hockey.

“When you saw him in juniors, he wasn’t someone you looked at and said, ‘He’s going to be a superstar in the NHL,’ ’’ says former junior opponent and future Bruins teammate Andrew Ference. “He was just a very kind of mediocre skater. He was just big.’’

There’s great footage showing how much Chara improved his skating and virtually every other aspect of his game as he became a regular with the Islanders and then a star with the Senators. In one clip, he stickhandles circles around then-Bruin Sergei Samsonov before scoring a nifty goal.

Chara has been the personification of the Bruins’ ideal for so long that it’s getting too tough to remember him playing anywhere else. He might as well be a franchise lifer. So it’s illuminating to hear his wife, Tatiana, say during the documentary there were some second thoughts about the decision to sign here during his first year in 2006.

“Did you ever have the feeling that oh gosh we’ve made a mistake,’’ asks Edwards about the first season under overmatched coach Dave Lewis.

“Oh, yes, that first year was difficult,’’ says Tatiana Chara.

It turned around, of course, with Claude Julien arriving in 2007 and recognizing how to properly deploy Chara. The Bruins won the Cup in Chara’s fifth season as a Bruin and have been a model franchise on his watch for more than a decade.

During our conversation, Edwards summed up Chara’s role in making the Bruins what they are.

“He has been such a consistent, high-level, fierce competitor,’’ said Edwards. “He has raised the bar for this team for so long. He has his own place in Bruins history and deserves all of the accolades that will be bestowed on him.’’

Chad Finn can be reached at chad.finn@globe.com. Follow him on Twitter @GlobeChadFinn.