OTTAWA — It was a rough start and a rougher finish.
The Bruins seven-game winning streak ended abruptly Thursday night, coincidentally to the team that helped spark the run.
Tim Stützle scored with 5:43 remaining to break a tie, then added an empty netter as the Senators beat the Bruins, 5-3, at Canadian Tire Centre.
Stützle squashed a spirited third-period comeback in the same building where Boston’s last loss came Oct. 27.
The Bruins (11-8-0) got goals from David Pastrnak and Mark Kastelic to pull even at 3 in the third before Stützle and the Senators (9-5-4) pulled away.
“It definitely felt like we had the momentum there for a second. We fought our way back into it and [in the second] intermission, I think we had all the faith in the world that we were going to make it a game and that’s what we did,” said Kastelic, the former Senator. “We stuck with it, but in the end, I think just kind of the little details and stuff that I think will be easy to fix [caught us].”
The Bruins caught a bad break right off the bat when Jeffrey Viel was called for tripping at the end of an impressive initial shift, where the Senators were on their heels. Viel got caught up with Drake Batherson, but the winger was actually spilled by teammate Nick Jensen’s stick.
The Senators, who went 4 for 5 on the power play in blowing out the Bruins, 7-2, last month, had been in an 0-for-19 slide with the man advantage. Claude Giroux changed that quickly.
Unmarked in the left circle, Giroux one-timed a slick backdoor pass from Stützle past Joonas Korpisalo just 1:28 in.
The Bruins had a chance to even things not long after when Mikey Eyssimont stormed down the right wing and scorched a wrister past Leevi Meriläinen, but it caught iron, clanging loudly off the cross bar.
It was the only real threat the Bruins mustered through the first 20 minutes.
The Bruins survived their second penalty (Mason Lohrei for cross-checking) with some timely checks and clears. Still, they could not build on that momentum and had trouble connecting on even the simplest breakout passes.
The Senators’ pesky forecheck paid off when Dylan Cozens, who was stationed unmarked between the circles, blistered a one-timer from Fabian Zetterlund to the top shelf past Korpisalo with just 57 seconds left in the period for a 2-0 lead.
The Bruins came out with some jump in the second, throwing their weight around plenty and landing plenty of pucks on Meriläinen’s cage. Big wingers Tanner Jeannot and Kastelic landed big thuds on the opening shift as they looked to re-set the tone of the game.
The Bruins’ physicality translated into room to roam and helped keep Ottawa’s forecheck in check.
“I think for us that’s kind of our bread and butter and I don’t think any of us were happy with our first period, that’s for sure,” said Kastelic, who landed a game-high five hits. “And when things aren’t going your way, I think the things you can control are just being physical and hard and then the rest will come from that.
“And I think that’s what we tried to do.”
Marco Sturm’s bunch finally broke through courtesy of some nifty tic-tac-toe passing from the top line.
Marat Khusnutdinov threw a cross-slot pass from above the left circle to Pastrnak, who settled it and slid it to Morgan Geekie, who redirected it past Meriläinen at the top of the crease for his 12th goal of the season.
“Anytime he’s got it, I just got to be ready,” Geekie said of Pastrnak’s feathery touch. “Khusty made a great play to get it over to him and yeah, I mean when he has a puck and a stick, he can kind of do whatever he wants with it, so just try to be in the right spot for him and put it in the net.”
Travis Green had apparently seen enough of the Bruins’ physical dominance in the period and sent little-used winger Kurtis MacDermid (4:21 of ice time, 5 penalty minutes) out to stir the pot.
MacDermid found a willing dance partner in Jeannot and the two scrapped at mid-ice. It amounted to a whole lot of nothing, with flurries of swings that didn’t land until Jeannot landed on MacDermid as the pair hit the ice.
The Bruins owned the period, but Ottawa still owned a 2-1 lead heading to the third.
An abysmal line change led to a Shane Pinto goal 1:06 into the third before Pastrnak (No. 402, good for joint fifth on the franchise’s all-time list with Rick Middleton) and Kastelic put the crowd on edge.
“The energy was good,” said Sturm. “It was just a lack of concentration and not sticking with what we were doing and those little mistakes. It’s a good team over there; they pressured our D very good.
“They’re doing a good job and unfortunately, we gave too many pizzas away today.”
Jim McBride can be reached at james.mcbride@globe.com. Follow him @globejimmcbride.