Islanders center Casey Cizikas, left, falls into the boards after...

Islanders center Casey Cizikas, left, falls into the boards after contact with Boston Bruins right wing David Pastrnak, right, in the second period of an NHL hockey game, Thursday, April 15, 2021, in Boston. Credit: AP/Elise Amendola

Three days of rest and practice yielded a rust-filled horrendous first period against the Bruins from which the Islanders could not recover.

"Unacceptable," coach Barry Trotz said. "They came out and set the tone and some guys didn’t want to accept the challenge."

The Bruins beat the Islanders for the first time in six tries, 4-1, on Thursday night before a crowd of 2,191 at TD Garden. It opened a three-game road trip, including another game in Boston on Friday night.

The Islanders (27-12-4), who remained two points behind the first-place Capitals in the East Division but just one ahead of the third-place Penguins, had not played since concluding a 5-1-0 homestand with a 3-2 overtime win over the Rangers on Sunday night at Nassau Coliseum.

They also played short one forward after Josh Bailey exited at 8:06 of the second period. Trotz did not have an immediate update on Bailey’s status.

"They came out hard, that’s really it, they came out flying," said Mathew Barzal, who misfired on a two-on-one chance at the right post off Jordan Eberle’s feed that could have tied the game early in the third period. "Their compete level was higher than ours tonight."

"I just thought our decision-making and our execution was poor," Trotz said. "And you can’t do that against the Boston Bruins because they’re a good checking team."

Semyon Varlamov, the only reason the game remained close as he made a season-high 41 saves, entered the game 5-0-0 against the Bruins with one shutout, a 1.57 goals-against average and a .949 save percentage. Meanwhile, Tuukka Rask, who stopped 22 shots, had missed 17 of the last 18 games with an upper-body injury and, in his only appearance in that stretch, lasted just the first period in a 4-3 overtime loss to the Islanders at Nassau Coliseum on March 25 before re-aggravating the issue.

Barzal’s failed two-on-one chance – the Islanders’ last, best chance to steal a point or two – instead turned into a clinching goal for the Bruins. Taylor Hall, with his first goal as a Bruin, immediately came up ice and put the puck through Varlamov’s pads for a 3-1 lead at 1:52 of the third period after the goalie tried to poke the puck away.

"Once they got the third goal I thought our level of play just fell right off," Trotz said.

"That was kind of a little bit of our game today," Travis Zajac said. "I don’t think we were executing as well as we need to, as hard as we need to be in some areas. They had some chances and they definitely deserved to win tonight."

Zajac scored his first goal for the Islanders in his fourth game since being acquired along with Kyle Palmieri from the Devils, cutting the Bruins' lead to 2-1 at 2:56 of the second period. Barzal, with a spinning feed from behind the crease, found Zajac open off the left post.

The Islanders were outshot, 23-7, in the first period – the most shots they’ve allowed in a period under Trotz – and outchanced 33-11 as the Bruins spent a combined six minutes, 10 seconds out of the opening 20 on the power play.

Brad Marchand, who also added an empty-net goal, gave the Bruins a 1-0 lead at 1:49 on a puck that deflected off his back and under the crossbar. Brock Nelson’s four-minute high stick on defenseman Mike Reilly at 14:49 negated the Islanders’ first power play and led to Craig Smith’s power-play goal to make it 2-0 at 17:55.

Said Trotz, "We need some more of our key guys going."

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