The 6-foot-4-inch, 234-pound Kastelic put a charge into the Bruins bench, and got the ol’ West End building rocking, when he tangled in the corner with Seider, the Red Wings’ slick 6-2, 215-pound blueliner, with 25 seconds to go in a scoreless first period.

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Only 4:25 into the next period, Geekie gained position in front of the Red Wing net and tipped home a long-range Elias Lindholm shot for the 1-0 lead.

“Nothing was planned, obviously,” noted Bruins coach Marco Strum, reflecting on what impact Kastelic’s fight, in which he leveled Seider with a right cross to the jaw, had on the bench. “But he wanted to get things going. And there was really no pushback from [Detroit] because we have more weapons, I would say, than them. It was good timing, I thought. Got the crowd going. Got us going.”

The fact that Kastelic chose to get into it with Seider — “A top young defenseman,” by Sturm’s account — was what added to the moment.

“It definitely got us going,” said Strum, “that’s for sure.”

“Just spontaneous — part of the game,” said Kastelic, reviewing the fight. “Just trying to play hard today.”

Kastelic noted he was somewhat surprised that the skilled Seider opted to oblige him in fisticuffs.

“He’s a good player, for sure,” said Kastelic. “And he’s a big guy, too, so I think he can hold his own.”

The Bruins mob goaltender Jeremy Swayman after he made 24 saves and stopped all three shootout bids he faced in the 3-2 win over the Red Wings.Mark Stockwell/Associated Press

The first off the bench for Boston in the shootout, Mittelstadt connected for the winner with a nifty backhand tuck at the right post on Red Wings goalie Cam Talbot.

Swayman, after making 24 shots in regulation, turned back all three Red Wing attempts in the shootout — including Lucas Raymond, Patrick Kane and, finally, Alex DeBrincat. The Red Wings, after that sleepy start of nine shots in the first two periods, outshot the Bruins, 17-5, over the final 25 minutes.

The Bruins were within two minutes of winning it in regulation when the Red Wings, with Talbot pulled for an extra attacker, squared it at 2-2. Michael Rasmussen knocked home the equalizer with a top-of-the-crease jam shot on a backhand feed from the right side by Kane at 18:06.

Geekie kept his groove going, connecting for both of the Bruins’ goals in regulation, including what looked like the game-winner with 6:21 remaining in regulation, for a 2-1 lead.

Now tied with Colorado’s Nate MacKinnon for the league lead in goals, Geekie hammered home his second of the night to break a 1-1 deadlock. About seven minutes later, the Red Wings pulled even on the scoreboard.

“I’m not supposed to be there,” said a humble Geekie, asked what it feels like to be in lockstep with McKinnon, the Avalanche superstar, for the league goal-scoring lead. “It’s fun. It’s cool. I used to watch that guy growing up. I know he’s not that much older than me, but he was in the league a lot before me. It’s cool, super fun, but it’s still early — a lot of the season left.”

Swayman finished out November with an impressive 8-2-0 record for the month and again looks every bit the franchise tender, following his choppy performance in 2024-’25.

“One shot at a time,” said Swayman, asked about his obvious boost in confidence the last month. “Just excited to be a part of it. Couldn’t be happier than to be a Bruin.”

Geekie, now with 20 goals in 27 games, is on pace for 61. He scored a career best 33 last season.

The last time he scored like he’s scoring these days?”

“Squirt hockey, maybe?” he said. “I don’t know… I have no idea.”

Kevin Paul Dupont can be reached at kevin.dupont@globe.com.