Don Sweeney and the Bruins’ quest to see a fully healthy blue line was dealt another setback Thursday, as the team announced that they will be without defenseman Derek Forbort for at least four weeks.

It could even be as long as a six-week recovery, according to the team, as Forbort underwent successful “open reduction and internal fixation surgery on his right middle finger.” Or, for my fellow stupid people out there, Forbort had a bad break in his middle finger and needed surgery.

The injury occurred in the first period of Tuesday’s win over the Penguins, and appeared to come when the 6-foot-4 Forbort took a blocked shot off the hand late in the period.

Word of Forbort’s extended absence came just hours after Bruins head coach Jim Montgomery noted that Forbort (and Jeremy Swayman) traveled back to Boston and would be out week-to-week.

One of several unsung heroes for the white-hot Bruins out of the gate this season, Forbort departs the Black and Gold lineup amid a start that’s included one goal, three points, along with 27 hits and 18 blocked shots, in 18:50 of action per game for Montgomery’s club.

Forbort, who is in the second year of a three-year, $9 million contract signed in 2021, has been especially valuable as the B’s go-to penalty-killing defenseman.

Averaging a team-high 3:36 of shorthanded time on ice per game for a league-leading Boston penalty kill, to say he’s been nails would almost be selling his contributions short. One of 58 NHL defensemen to play at least 25 shorthanded minutes in 2022-23 at the time of his injury, Forbort ranked 10th in on-ice shots against per 60, and seventh in on-ice high-danger chances against per 60.

With Forbort unavailable for Thursday’s game in New York, the B’s turned to Mike Reilly as their next man up.

Paired with Anton Stralman for much of the night, the 6-foot-1 Reilly finished Thursday’s victory with one hit and a minus-1 rating in 16:51 of time on ice, and had a solid denial of a two-on-one chance from the Rangers late in the second period of an at the time tied contest.

It was Reilly’s first game action since Oct. 25, and broke up what’s been a series of papers transactions with Reilly shuffled between Boston and Providence with the Bruins maximizing Reilly’s 24-day waiver-free window of movement after the veteran defenseman cleared waivers before the start of the regular season.

“I just come to the rink every day with a good attitude,” Reilly said before Thursday’s game. “That’s what I’ve been trying to do every day when I want to come to the rink and just work on my game. That’s what I’m focused on. And there’s times you want to kind of think ahead a little bit in the future and what not.

“But now there’s an opportunity and you just come to the rink every day with a good attitude and come to work,” said Reilly.

In addition to giving Reilly an opportunity to recarve out a role here, Forbort’s injury will also presumably delay the front office’s need to shed salary to activate Charlie McAvoy off the long-term injured reserve.

Assuming Forbort and Swayman are moved to the long-term injured reserve, the Bruins would have just enough money to activate McAvoy without having to make a trade.

The Bruins would still have to move someone upon Forbort’s return, but that’s of course assuming that the Bruins are fully healthy on the backend. Something that’s been easier than done in 2022-23.