One of the great unknowns coming into this season was how the Bruins would fare with the loss of their top two centermen, Patrice Bergeron and David Krejci. One is headed to the Hockey Hall of Fame at some point, and the other should have his number raised to the Garden rafters. Not easy guys to replace.

But so far, they’ve managed just fine. Coyle has set career highs in goals (25) and points (33) while Zacha has set a career high in assists (37) and his 56 points heading into Tuesday’s game was one off his career high.

Zacha in particular has caught fire lately. He went into Tuesday’s game with a six-game point streak (2-7-9) and points in 12 of his last 14 games skating primarily on a line with David Pastrnak and Danton Heinen.

The playoffs will be another proving ground for Zacha, taken with the sixth overall pick by the New Jersey Devils in 2015, but so far the transition from a couple of foundational players has been as painless as one could possibly hope for. And, after some growing pains in the role, Zacha’s feeling pretty good about what he’s been able to accomplish.

“It was an exciting season for me from the beginning, getting the chance to play a lot of minutes and moving back to center where I feel the most comfortable and just playing the game that I wanted to play,” said Zacha. “Last year was a little bit more focus on offense form the beginning and this year I could also focus on my defense and getting better within my game. There were some ups and downs, too, with me and the whole team. But I think that’s what made me feel good within the season and getting for the playoffs.”

In his first season with the Bruins, coming form Jersey for Erik Haula in the offseason (a deal that’s looking more and more like a steal), he was mostly one of Krejci’s wings with Pastrnak on the other side. Moving back into the middle, he knew he had to focus on his defensive game, especially with what’s asked of the centers in the B’s defensive system. But he soon realized that that’s not all that was being asked of him.

“I feel like as center, you focus a little bit more on defense at times and not too much performing with points,” said Zacha. “I think there were a couple of games where I completely forgot that that’s part of the game that I also have to be performing, being a top six. Playing with players that I’m playing with, I have to perform in that direction, too. But they helped me a lot. Pasta’s been on a roll all season and it’s helped me be where I am today.”

Zacha is also proving himself to be a decent faceoff man. He’s not quite pulling it back at 61% like Bergeron did last year that, but he was up to 54.9% going into Tuesday. That’s up from 45.3% in limited work last season.

“It’s very important, especially if I want to be starting power plays on my side and winning those faceoffs is important and even the penalty kill and the 5-on-6 situations I’m put in,” said Zacha. “To have the trust there, I have to perform in the circle and I’m happy. At the start of the season, I said I wanted to work on that and it’s getting better. It’s something I want to pride myself in, to have a good faceoff percentage. I just have to work on that.”

He said video work has helped him improve, as well as the repetition.

“When you play on the wing and get thrown in two, three times, max, it’s kind of hard to get the timing right,” said Zacha.

Zacha puts a lot of value on having the opportunity to play with and learn from one of the league’s best two-way players in Bergeron. The former captain’s level of play is to what he aspires. But he doesn’t feel like either he or Coyle are in anyone’s shadow.

“Especially at the start of the season with all the talk of me and Charlie taking over those two spots, you were thinking about it more,” said Zacha. “Now it’s more about just getting the best out of us and focus on that.”…

Coach Jim Montgomery had toyed with the idea of going back with Linus Ullmark on Tuesday just to give him a look at Carolina, but he kept the rotation going with Jeremy Swayman.

“I’m going with what’s worked,” he said in the morning.

That, of course, set off another round of questions about how he’d work his goalies come playoff time. And while he’s not committing to anything just yet, he made an argument for keeping a rotation, even though he admitted it’s “uncharted territory.”

“I won a national championship (at Maine) with Mike Dunham and Garth Snow alternating all throughout the year and I know that, as a player on that team, we were incredibly comfortable,” said Montgomery. “I know it’s a different league but it was a championship team nonetheless. I know there’s no Frozen Four team alternating their goalies, but it’s the makeup of your team. It’s the strongest position (of the Bruins).”

Montgomery said he’s not worried about the Swayman and Ullmark balking at a possible rotation.

“Both of them want the net, but I think if you look at the success we’ve had the last two years, they’d be fine with it. Because they’re great teammates. The core of the decision is a lot easier when there’s no animosity between the two and they support each other so well,” said Montgomery.

Ullmark playfully danced around the topic. While he said if he ever said he didn’t want the net “I should just retire,” he’s willing to go with whatever is successful.

“If it works, it works. That’s all I’m going to say. I’m 100 percent confident in my abilities, as much as I have confidence in Sway’s abilities as well,” said Ullmark….

Montgomery said Maroon remains on track to make his Bruin debut on Saturday in Pittsburgh.