Boston left wing Brad Marchand, top, drops Florida defenseman Nate Schmidt to the ice during a fight in the first period of Monday’s game in Boston. Charles Krupa/Associated Press

No Sasha Barkov? No Matthew Tkachuk?

No problem for the Florida Panthers, who still managed to get under the skin of the Bruins and come away with a 4-3 win over Boston without Barkov (ankle) and Tkachuk (illness) at TD Garden in a Monday matinee.

After A.J. Greer caught David Pastrnak with a questionable hit from behind in the first period, the Bruins started taking undisciplined penalties and soon found themselves in a game of catch-up that they are currently ill-equipped to win.

“Again, they’re winning the mental side of the battle on us,” said Coach Jim Montgomery. “Pasta got hit and I love what (Pavel Zacha) did, he went in and defended him. That’s great. But the penalties after that? It’s just not disciplined. And it’s all four games that we take at least four minors. Can’t win hockey games that way. And we can’t lose as many battles as we do. I mean, they’re the standard right now for winning battles. We’re not up to that level yet and we have to vastly improve our level.”

Captain Brad Marchand downplayed the lack of discipline.

“I didn’t think it was that bad tonight. There’s other areas where I’m more concerned about,” said Marchand. “Our compete level, attention to details need to be a little better. We need to win more battles. It’s definitely something that they had the edge in tonight. If we do that, our game will be back where we want it.”

While the Bruins got beaten for a Florida power-play goal, they went 0 for 4 on their own power play and also gave up a short-handed goal. Boston is 2 for 18 on the power play to start the season.

“Lost battles,” said Montgomery. “It’s the same thing. We’re not coming up with enough pucks so we’re not getting any O-zone time if you’re not winning draws and not executing on your entries.”

The Bruins went into the game with a focus to keep their cool after going haywire in the season opener in Florida last week, but it didn’t take long for them to lose it. And as usual, you could see their reasoning.

After Johnny Beecher scored on a deflection of a Mark Kastelic shot and then Anton Lundell evened it up on a 4 on 4 off a bad Mason Lohrei pass, the former Bruin Greer hit Pastrnak close to the boards. Pastrnak did not hit the boards but did get checked into a Panther and he was slow to get up. By then, Zacha and Greer had dropped the gloves and were sent to the box.

On the next shift, Charlie McAvoy crosschecked Carter Verhaeghe and was given a two-minute penalty. The Panthers needed just six seconds of it for Sam Reinhart to beat Jeremy Swayman over the blocker from the slot.

Still, Pastrnak wanted his pound of flesh. A minute after the Reinhart goal, Pastrnak lined him up in the Florida zone and blasted him. It was a clear interference, and Nate Schmidt tried going after Pastrnak. But Marchand jumped in and took Schmidt to the ice.

In the second, the Bruins tied it up at 5:08 when Brandon Carlo beat Sergei Bobrovsky with a high wrister. But Florida came up with Reinhart’s short-handed goal at 9:39, and Lundfell extended the lead at 12:59. Lohrei scored the final goal at 14:07.

In the scoreless third period, the Bruins pulled Swayman with 1:57 left in regulation, but Pastrnak was called for slashing with 49 seconds left to end the hopes of a comeback.

DEVILS 3, UTAH 0: Jake Allen registered his first shutout with New Jersey and rookie defenseman Seamus Casey scored early in the second period as the Devils downed the visiting Utah Hockey Club.

Stefan Noesen and Nico Hischier also scored for the Devils, who won for the fourth time in five games. New Jersey missed the playoffs last year.

Utah lost for the first time in four games. It won its home opener over Chicago, then defeated the Islanders and Rangers in overtime to start its current road trip.

SENATORS 8, KINGS 7: Josh Norris capped a two-goal effort with the game-winning goal 56 seconds into overtime as Ottawa beat visiting Los Angeles.

Zack MacEwen also had a pair for the Senators, with Jake Sanderson, Drake Batherson, Thomas Chabot and Claude Giroux also chipping in.