When Mark Kastelic suits up every night, the Bruins know exactly what what they’re going to get from the rough-and-tumble forward.

Now Kastelic knows what he’s going to get from the Bruins.

The B’s announced on Friday that they inked the 25-year-old Kastelic to a three-year extension that carries an annual cap hit of $1.567 million.

Arriving in the offseason in the Linus Ullmark trade that also brought goalie Joonas Korpisalo and a first-round pick (Dean Letourneau), the 6-foot-4, 227-pound Kastelic has shown that he not only has Bruin bloodlines (his late grandfather Pat Stapleton played for the B’s in the 1960s) but that he also understands what Bruin hockey has been all about it when it’s going good.

Primarily a fourth-line center who has bumped up to third line on occasion, Kastelic leads the B’s in hits (151), makes his presence felt in front of both nets and is not afraid to drop the gloves when the occasion calls for it. He’s also an effective centerman, winning 55.2% of his draws and pitching in offensively at times with 4-7-11 totals in 39 games.

The signing of Kastelic removes just one question mark that GM Don Sweeney faces.

Still unsigned for next year are unrestricted free agents-to-be Brad Marchand, Trent Frederic, Justin Brazeau,  Parker Wotherspoon, Marc McLaughlin and Cole Koepke, while decisions also have to be made on pending restricted free agents Morgan Geekie, Oliver Wahlstrom, John Beecher and Mason Lohrei.

Marchand, the captain who has been working on a team-friendly deal ($6.125 AAV) for the last eight years, and Lohrei, a promising offensive defenseman, should be top priorities to return, while Brazeau is making a strong push for an extension. But the NHL calendar may put those on the back burner for a bit.

The biggest question is what will the B’s do with Frederic? He was coming off career highs in goals (18) and points (40) last season, but he has not been able to produce offensively for a team that needs it desperately. He’s got just 5-6-11 totals in 40 games.

Frederic, who’ll turn 27 on Feb. 11, is a well-liked, team-first personality, and Sweeney said in the club’s preseason presser that he’d begun discussions with Frederic’s camp on an extension, as well as Geekie’s and Marchand’s.

That, of course, doesn’t mean a deal is imminent or even gets done. If Frederic’s production remains status quo and some team offers the B’s something of high value for the center/wing before the March 7 trade deadline, there seems little doubt that Sweeney would listen.

But if Frederic picks it up, that could change. Right now, he is doing what the offense-deficient team needs of him, playing third line center, though he’s been most effective at wing in his Bruin career. He’s played better the last couple of games, though it hasn’t led to offensive production.

So the Frederic decision still looms for Sweeney and the Bruins. But with the Kastelic signing, one necessary bit of business has been completed.