When he looks in the Bruins’ space this season, he sees a group that cares about each other. A group that has each other’s backs. It was not something he always felt during the tumultuous 2024-25 season that included a plethora of departures that included the coach, the captain, and a cadre of veteran leaders.

Leach credits Marco Sturm for helping to bring the cohesiveness back to Boston.

“The biggest thing for us, I think, as the coaching staff has been, if you wanted to talk about from last year to this year, it’s a marked difference in our attitude and our competitiveness,” Leach told the Globe recently. “And we have players in there that love coming to the rink and working with each other, and whatever it was last year, the vibe was not where it used to be. And Sturmy has brought in a level of energy that’s been infectious and you see it.”

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Leach played parts of five seasons with the Bruins, Lightning, Devils, Canadiens, and Sharks, before hopping behind the bench, first in the Deutsche Eishockey Liga, then American Hockey League, before moving to the NHL. He knows the burdens and stresses of hockey at the highest level.

“I think the one thing I’d also say, coming back into the organization and really as my first time as a coach with the Bruins — not the Providence Bruins — there’s a lot of pressure with Boston and playing in front of that crowd,” said Leach. “And I think last year was really challenging for guys, and I think they felt a bit like they were on an island a lot of nights. There wasn’t that camaraderie that I think we have this year. We’re going to go through all the challenges. It’s going to happen. It can be hunky-dory now. And then as we all know, it changes. But I do think they have a belief in there that when we go through the stuff that’s not as fun, at least you’ve got 18, 19 other guys that are willing to go in there with you as opposed to, I think, there was some of that was missing last year.”

A defenseman by trade, Leach works with the Bruins blue liners and also organizes the club’s penalty kill. Preparation, as always, is a huge part of an assistant’s job. It’s a huge part of Leach’s responsibilities, especially on game day.

Prior to morning skate, Leach holds a penalty-kill prescout before heading on the ice. The Bruins run a diamond (or 1-2-1) penalty kill, which emphasizes clogging the middle. The Bruins are the most penalized team in the league (522 minutes), and the kill has had its ups and downs — ranking 19th at 79.2 percent.

Sturm appreciates the passion Leach brings in his teaching.

“You can see those guys take a lot of pride in what they do, and you can tell on the penalty kill, when it’s good and when it’s bad, [Leach is] all in,” said Sturm. “He works extremely hard. He wants to be the best.”

Leach had played some diamond during his days but there are variations, and Sturm said Leach did his homework so he’d have a firm grasp of what Sturm wanted when camp opened.

“When I talked to him in the summer about that, I think he had to do a lot of research about it because yes, you played that, but also everyone has different jobs and the details in those diamonds these days, just a little bit different or the way I wanted to do it,” said Sturm. “So, I think that’s something he needed to get more information out of me or some other coaches around the league, see how they do it and what’s important, what’s not.”

If it’s not a full-team morning skate, Leach and fellow assistants Chris Kelly and Steve Spott will run the drills.

“Most of our skates in the morning are optional, so usually the three of us, Kells, Spotter, and I, will figure out what we’re going to do,” said Leach. “We’ll skate them and then get them off the ice and then go home for a bit.”

Leach gets back to the rink around 3 p.m. for another round of meetings and prepares for the pregame meeting with the players at 5:30.

“I’ll meet with the D a little bit then, too, just to get them prepared for who we’re playing that night,” he said. “And then it’s on.”

Jim McBride can be reached at james.mcbride@globe.com. Follow him @globejimmcbride.