Mason Lohrei was three minutes away from the long Providence to Pennsylvania bus ride when he got the call he’s been dreaming of his whole life.

“We were actually packing the the bus to go to Wilkes-Barre and I filled up a cooler and was carrying it outside when our equipment guy grabbed the cooler from me and said, ‘Hey, go into the coaches office.’ It was was 12:27 and the bus left at 12:30,” said Lohrei.

Lohrei, the Bruins’ second-round pick from 2020 and their best defense prospect, got the word he will make his NHL debut on Thursday night against the Toronto Maple Leafs at the Garden, thanks to a set of circumstances that could see the B’s miss half of its regular defense corps.

Charlie McAvoy will start his four-game suspension, Matt Grzelcyk was placed on long-term injured reserve and Derek Forbort is nursing a lower body injury, making him a question mark for the Leafs’ game. An offensive-minded defenseman who’ll need to grow his game in his own end, the 22-year-old Lohrei had four assists in seven games with Providence.

Defensemen Ian Mitchell and Parker Wotherspoon were also recalled from Providence.

Given the situation, Lohrei will not have the opportunity to be eased into the lineup. He will be paired with Brandon Carlo and play in the top four. The two lanky D-men, both of whom are 6-foot-5, played together in the preseason.

“I just liked their length, their mobility and their ability to force a lot of dumps-in and kill a lot of plays before it even gets into our end,” said coach Jim Montgomery.

“You’re going to see (Lohrei) out there a lot. We think he’s ready for this league and we think he’s going to play well in this league. I don’t know what the minutes are going to be, but he’s going to be playing top four minutes, so it should be anywhere (around) 18, depending on the special teams.”

It doesn’t seem so long ago that Carlo was the young pup being led into battle by Zdeno Chara. Now he’s the mentor and, considering that Grzelcyk is now on LTIR ( a player must miss 10 games and 24 days to qualify), it appears Lohrei will get a good, long look.

“It’s crazy being in this position. The time frame for me being in this position has gone by so fast. I still feel like a young guy at times but overall, I think the biggest things I’ve learned from Z, especially in these early stages of playing together, is communication on the ice,” said Carlo. “As long as we’re doing that, we’re going to set things out in the defensive zone and through the neutral zone and whatnot. And when we get back to the bench, if he sees something that I should do differently, then that’s the way you build chemistry for pairings. I think for both of us just communicating as much as possible (is key). He’s a smooth skater, great player and he’s going to do just fine. I think just helping him maybe manage nerves at times, I’ve been in the position and it’s about not getting over-exaggerated and overthinking too much. That’s a big thing in my game makes me play better. Just trying to keep him calm there and be a positive, encouraging voice and I feel that from there, he’s just going to take it and run with it.”

As for the butterflies, Lohrei doesn’t deny that they are there, but he’s leaning into them.

“Since I got the call up there’s been nerves, but that’s all part of and that’s what makes it so special and so fun,” said Lohrei.

Leaning on Lindholm

With the loss of McAvoy, Montgomery will lean heavily on Hampus Lindholm. That might not be such a bad thing. When McAvoy was injured to start last season, it was Lindholm’s excellent performance that sent the B’s on their way to a record-breaking regular season.

“I think the two of them when they’re in the lineup give us an advantage over most teams just because they control the game when both of them are out there,” said Montgomery. “And the opportunity not only with (McAvoy) but with Forbort out, now he’s goes to the No. 1 PK. He’s going to be out there for almost every D-zone draw when we have the opportunity, he’s going to be out there for half of the O-zone draws…. Him playing 26 to 28 minutes would not be a surprise now.”

As for Forbort, Montgomery quickly corrected himself by saying he is questionable, but make of it what you will.

Suspension talk

Montgomery’s take on McAvoy’s suspension for his high hit on Oliver Ekman-Larson?

“The league does an extensive review,” said Montgomery. “All I know is I would not want their job. I don’t think you can win, whether it’s too long or too short. We respect the job that they do and we’re going to respect their decision. I’d like to have him back sooner, but I coach him.”

Loose pucks

Matt Poitras will play his 10th game on Thursday against the Leafs, thus burning the first year of his entry level deal. He got the word from the GM on Tuesday.

“(Don Sweeney) just called me up to his office and I kind of had an idea it was going to be good news. I was still a little bit nervous, but he said, ‘Yeah, you’re going to be sticking around for your 10th game, just keep working, keep preparing the same way and you’ll be fine,’ ” said Poitras.

The 19-year-old rookie has been living in a hotel since training camp, but that’s going to change.

“Yeah, a couple of options have been presented, but I’ll take some time and talk to my parents and see what they think,” said Poitras.

It looks like Poitras will be playing a marquee role against his hometown team, the Leafs. He finished the emotional comeback win against Florida skating on a top line with David Pastrnak and Pavel Zacha and that’s the line he practiced with on Wednesday.

“Those two guys are really skilled players and for me it’s kind of easy to find spaces and they’ll be able to move in and make plays and feed me the puck and I can feed it right back,” said Poitras. “Obviously, Pastrnak is a really good goal scorer and I see myself as a playmaker, so I’ll be looking for him and he can do his job and score.”…

Jakub Lauko was placed on IR. He has not skated with the team since taking in errant skate to the head over a week ago in Chicago. … After posting eight goals, six assists and a plus-nine rating, Pastrnak was named the NHL’s third star for October.