The Bruins (20-16-1) lost for the third straight time on this five-game homestand that wraps up Tuesday against the Canadiens. What follows is a much-needed three-day Christmas break for a team that looked worn out against Ottawa.

Fabian Zetterlund (two power-play goals, assist), Drake Batherson (goal, two assists), and Dylan Cozens (goal, two assists) paced the Senators offense.

The visitors set the tone early, skating short, speedy shifts and keeping the Bruins on their heels for the majority of the first period, which ended with Ottawa holding a 3-1 lead.

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The Senators consistently got to the greasy areas in front of the net and in the corners. They outworked the Bruins to loose pucks and outbattled them on 50-50 plays.

“They scored a lot of goals tonight in front of the net and that’s something that we work on. We take pride in it. If you’re going to be a good defensive team in this league, you’ve got to take pride in it,” said Charlie McAvoy, who had one of Boston’s goals. “So, we just know better as a group, what we have to do and how you’ve got to play to win in this league.

“And getting beat at your net front — it’s any team in this league — if you’re getting beat at your net front, you’re not going to have success. You’re going to give up a lot of goals, and that’s what we did tonight.”

Ottawa’s Jake Sanderson (85) checks Bruins forward Fraser Minten hard into the boards Sunday. CJ Gunther/Associated Press

Both teams were on the second half of back-to-backs, so any fatigue factor was equal. Ottawa coach Travis Green, the one-time Bruin, wisely employed the short-shift strategy.

It took the Senators just 90 seconds to take the lead. Batherson collected a touch pass from Cozens and wristed one from between the circles past Joonas Korpisalo, who was screened by David Perron.

Claude Giroux doubled the lead at 13:44, cashing home a rebound after Korpisalo had made impressive back-to-back saves in tight. Ottawa pushed the advantage to 3-0 with a power-play strike from Zetterlund, who snuck a wrister past Korpisalo from the left dot.

The goal set off a chorus of boos from the restless Garden denizens.

Consecutive penalties to Tim Stützle (hooking) and Artem Zub (tripping) gave the Bruins a late five-on-three power play. David Pastrnak finally gave the fans something to get excited about when he whistled a half-slapper over Linus Ullmark’s blocker with 52.4 seconds left in the period.

The middle frame started with the Bruins holding 40 seconds of carryover power-play time, but they couldn’t generate a chance. They did come out with some bees under their bonnets, however, with Pastrnak, Fraser Minten, and Tanner Jeannot landing big hits in the opening moments.

They couldn’t maintain the momentum, and the Senators soon regained control, striking twice quickly to run their advantage to 5-1.

Stützle hit first — his fifth goal against the Bruins this season — followed by a seeing-eye score from Cozens at the point.

The boo birds came out again and so did Korpisalo, who was pulled in favor of Jeremy Swayman after giving up five goals on 17 shots.

“Well, you never want to get pulled. Doesn’t matter what happens,” said Korpisalo. “Today was one of those days and obviously I’m not happy with how I played. If you play well, I don’t think you get pulled.”

Jeannot tried to breathe some life back into the building, but his heavyweight bout with enforcer Kurtis MacDermid was shortlived and uneventful.

A glimmer of hope came in the form of McAvoy’s goal at 14:36, but Zetterlund restored the four-goal advantage with his second at 17:26.

Things got chippy and heated in the third, with Mark Kastelic fighting MacDermid and Pastrnak and Ridley Greig dropping the gloves and getting hit with roughing minors and 10-minute misconducts.

Cozens received a two-minute kneeing penalty on Bruins defenseman Nikita Zadorov and both received 10-minute misconducts.

Bruins tough guy Mark Kastelic scraps with Senators counterpart Kurtis MacDermid in the third period.CJ Gunther/Associated Press

It was a fitting end to an ugly night.

“You’ve got to expect [it], guys in this room hate losing,” said Zadorov about the bad blood in the third. “I think that’s what happens.

“It’s not where we want to be, we lost the last three at home. It was a big stretch for us, so it’s unacceptable from our side, and we just throw in the emotions, I think.”

Jim McBride can be reached at james.mcbride@globe.com. Follow him @globejimmcbride.