Additionally, top defender Charlie McAvoy (facial surgery) remains on IR as well, while Jordan Harris (right ankle fracture) is on long-term IR.

The Bruins will need to summon another defenseman from Providence, with Sturm indicating it likely will be either Frederic Brunet or Victor Soderstrom.

“Well, we’re slowly running out of D, down [in Providence], too,” said Sturm, who has Jonathan Aspirot, who started the season with the Baby Bs, as a fixture in his rotation now.

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Callahan left in the first period Tuesday, and the Bruins were further shorthanded when Nikita Zadorov missed the final 12-plus minutes when he was hit with roughing and misconduct penalties.

The circumstances forced Aspirot to play on his off side, which can be considerably more challenging to play and frustrating to watch.

“On one side of it … you’re so mad and you want to scream at them, but on the other side, you have to remind yourself they’re doing everything they can. They really do. They try everything they can, and we are asking a lot for them,” said Sturm. “We put them in a lot of difficult situations or positions and yeah, they’ve never really done it before. So that’s where we’re at right now and that’s why we use today, not on the ice, but use today as more like a teaching or video [session]. Try to teach it that way without being tired on ice and hopefully we do a better job.”

Aspirot played a career-high 21:14 against the Red Wings and scored his first career goal. A left shot, he spent considerable time on the right side.

“It’s a little different, a little adjustment, but I try not to overthink the game and just play it as it is,” said Aspirot.

Now 15 games into his NHL tenure, Aspirot’s simple, steady, and physical play has been a welcomed addition.

“I try to use my feet as much as I can and close the gap and play hard,” said Aspirot. “So, I think if I keep doing that, it fits well in the system.”

Sturm said the timing was right for Aspirot, who spent seven-plus seasons in the AHL.

“He fits the style because he can skate, he can close, he can do a lot of things just the way we want to defend,” said Sturm of his hybrid system that combines elements of man and zone concepts. “And if you look at some other teams, just like Vegas for example, they [play more zone]. So, that would be a totally different story, and I don’t know if that would be a good fit for him, I’ll be honest.

“So, I think he just got here at the right time. Probably with the right coach, too, with the right system. Sometimes you just have to be lucky, too.”

…

As for the possible callups, Brunet is a left-shot defenseman whom the Bruins drafted 132d overall in 2022. He has four goals and five assists in 20 games with Providence. Brunet played in one game for the varsity last season . . . Soderstrom is a right-shot blue liner with a goal and eight assists in 18 games with the Baby B’s. Soderstrom, the 11th overall pick by the Coyotes in 2019, has 53 games of NHL experience under his belt — all with Arizona. The Bruins acquired Soderstrom in June from the Blackhawks in exchange for defenseman Ryan Mast and a 2025 seventh-round pick . . . Whoever gets the call, he will be the 10th defenseman to don Black and Gold this season . . . If the Bruins go the trade route, keep the name Pavel Mintyukov in mind. Sportsnet’s Elliotte Friedman reported recently that the 21-year-old Ducks defender would welcome a trade after a few healthy scratches. He was the 10th overall selection in 2022 . . . The Bruins sent forward Riley Tufte to Providence . . . Former Bruins coach Jim Montgomery returns to Boston Thursday. His Blues come to town at 9-11-7.

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