Jean-Gabriel Pageau scored twice and Semyon Varlamov made 28 saves as the Islanders extended their point streak to six games (3-0-3). Jordan Eberle also had a goal and an assist and Leo Komarov chipped in with two assists.
''I thought we played an Islanders-style playoff game against the Bruins,'' New York coach Barry Trotz said. ''I thought we were moving our feet, I thought we were physical, I thought we were winning our battles. It was a big win for us. That's a very good team over there.''
Brad Marchand and Patrice Bergeron scored for Boston, and Tuukka Rask stopped 38 shots but the Bruins' five-game winning streak came to an end. David Pastrnak added two assists for Boston, which lost for just the second time this season in regulation - both against the Islanders.
With the game tied at 2, Islanders captain Anders Lee corralled a pass in front of Rask and delivered a cross-ice pass to set up Barzal at 5:30 of the third period. The 23-year-old center extended his point streak to eight games. Eberle assisted on the power-play tally.
Pageau extended the Islanders' third-period lead to two goals with a short-handed score at 14:32. Komarov intercepted a loose puck at the Islanders' blue line to start the sequence. Pageau has 14 short-handed goals since the 2014-15 season.
''We can be happy about it, but we don't want to be satisfied,'' Pageau said of the victory. ''Every game matters, every game is important. We need as much points as we can to keep climbing. It was a huge two points for us tonight.''
The Bruins' only other regulation loss this season came against the Islanders on Jan. 18th.
Bergeron evened the score at 2 with a nifty wrist shot at 16:51 of the second period. Marchand and Pastrnak assisted on the play.
''Games are tighter, it's closer to playoff hockey,'' Bruins coach Bruce Cassidy said. ''You are not going to get those typically wide-open games that you might get early in the season.''
The Islanders scored twice within 3:26 to erase a one-goal first-period deficit. Pageau banged home a rebound at 11:26 of the first period. Defenseman Ryan Pulock tossed a puck on net from a sharp angle to create the rebound opportunity. Komarov also assisted.
Eberle's shot from the outside trickled past Rask at 15:16 to give the Islanders a 2-1 edge. Brock Nelson assisted on the play and became the 22nd Islanders player to reach 300 career points with the franchise. Defenseman Scott Mayfield picked up the secondary assist.
''We are detailed in our own end and we limit the chances we give other teams,'' Eberle said. ''As long as we are on top of pucks and we're not giving them too much, most nights we have a chance to win.''
Marchand opened the scoring at 8:41 of the first period when Bergeron found him all alone in the slot and the savvy winger netted his 299th career goal.
''Played a great team, a team that is very hard on the forecheck,'' Bergeron said. ''They got a lot of turnovers out of it and created a lot of chances.''
Boston defenseman John Moore made his season debut.
The Bruins were originally slated to have two games against the Devils next week, but both have been postponed due to COVID-19 protocol. Boston will enjoy a rare week-long break during a truncated 56-game season.
STARTS AT THE TOP
Trotz and Islanders general manager Lou Lamoriello have 2,150 combined wins, the most by any duo in NHL history. Trotz recently surpassed Ken Hitchcock for sole possession of third place on the league's all-time win list.
Marchand is one goal short of his 300th. . Rask is three wins shy of his 300th NHL victory. . David Krejci needs four points to reach a career total of 700. . Pastrnak skated in his 397th career game Saturday.
Islanders: Visit the Buffalo Sabres on Monday.
Bruins: Travel to Lake Tahoe to play against the Philadelphia Flyers on Feb. 21 in one of the NHL's two outdoor games this season.
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