As is tradition, the Bruins are rapidly reaching deep into their defensive bag.

Beginning the year without both Matt Grzelcyk and Charlie McAvoy available, the Boston blue line took another hit Saturday night when the Coyotes’ Liam O’Brien rocked Brandon Carlo off the glass to the right of the Black and Gold’s net. And as Carlo made his way down the tunnel and the B’s locker room, it didn’t take long for the word to come down from the Bruins. Upper-body injury, done for the night.

Oh boy.

The 6-foot-5 Carlo’s history with the ‘upper-body’ injury — and one upper-body injury, to be exact — is no secret, and it’s enough to make you wince.

Carlo suffered four concussions in a 50-month span from 2017 through 2021, and even had a weird incident last April where he took a heavy hit one game, played just five minutes in the team’s next outing, and then missed another contest with an undisclosed injury.

While the Bruins wouldn’t (and still haven’t) confirm that it’s a concussion — that’s the real ‘C’ word in the NHL in 2022, and almost no coach or management figure says it anymore, unless they’re out there trying to publicly lobby for a suspension on the play that ended with their player suffering a concussion — it’s hard not to be concerned about this being exactly that.

Sunday’s practice at Warrior Ice Arena did little to silence those concerns.

Not only was Carlo not on the ice, but the team had little to offer in terms of a concrete update on his status.

“He’s better today than we were expecting, so we’re hopeful,” Bruins head coach Jim Montgomery said when asked for the latest on Carlo. “But he’s still not ready to go.”

Montgomery also made it clear that the Bruins are not going to put any sort of timeline on Carlo, who had been playing as the team’s top right-side defenseman, as it stands right now.

“There’s gonna be no rush, that’s for sure,” Montgomery admitted. “It’s just like there’s no rush for [Grzelcyk], or [Brad Marchand], or when [Charlie McAvoy] starts skating with the team. We’re gonna do it when it’s right for them but in the long term that’s what’s right for the Bruins.”

So, now what?

With Carlo unavailable for Sunday’s practice, the Bruins recalled Dan Renouf from Providence.

One of the final cuts from B’s camp, the 6-foot-2, 205-pound Renouf made three preseason appearances with the Bruins, and totaled one shot, seven hits, and two blocked shots in his training camp run with the team.

He’s not a direct replacement for Carlo in the sense that he’s a left shot whereas Carlo is a right, but it’s close enough for the Bruins to make that call to Providence.

“We felt in camp [Renouf] was the one that was most like a steady, stay-at-home defenseman that can defend really well and help us break pucks out,” Montgomery said. “Very similar to [Carlo].”

Renouf finished with a plus-1 rating debut in his P-Bruins debut Friday night, and returns to the NHL with 23 games of NHL experience between the Red Wings and Avalanche.

The easiest fix, of course, would’ve been putting Anton Stralman to the right of Hampus Lindholm on Boston’s top pairing. After all, the duo had an extended stretch together in training camp, and they actually looked like a solid fit (Montgomery seemed to like how the Swedes worked in tandem).

But the 36-year-old Stralman is still dealing with some visa issues that are unlikely to be resolved in time for Monday’s head-to-head with the Panthers at TD Garden.

“We haven’t expedited [Stralman’s] visa yet,” Montgomery offered. “I mean, he needs to get his kids too, so they’re hopefully flying to Canada today at some point so that we can get that done.”

The issue, as Montgomery explained, is that you need to leave the country you’re going to live in to get the visa done and cross back over the border, which means that Tuesday night in Ottawa may be the next-best chance for the Bruin to get Stralman fully cleared and ready to join the roster.

“I’m very hopeful [Stralman plays in Ottawa], but that expediting thing is a little bit of an issue,” said Montgomery.