Panthers right wing Juho Lammikko and Islanders defenseman Adam Pelech both go...

Panthers right wing Juho Lammikko and Islanders defenseman Adam Pelech both go for the puck during a game Saturday in Sunrise, Fla. Credit: AP/Brynn Anderson

SUNRISE, Fla. — The Islanders’ power play is struggling to produce. And it’s costing them.

“It’s one of those games where you look back on it and we kind of let it slip again,” Anders Lee said. “That’s what makes this frustrating.”

The Islanders — who went 0-for-4 with the man advantage and are in a 1-for-19 rut in their last five games — lost to the Panthers, 4-2, on Saturday night at BB&T Center for their third straight defeat.

Mathew Barzal scored a goal but fell one point shy of becoming the 11th player in the last 25 seasons to compile 100 points in his first 100 NHL games. Robin Lehner made 27 saves for the Islanders (8-6-2) and Roberto Luongo stopped 29 shots for the Panthers (5-5-3), who have won three straight since their No. 1 goalie returned from a lower-body injury suffered in the season opener.

“I think it’s small things,” defenseman Ryan Pulock said of the Islanders’ struggles. “It’s just little mistakes here and there have kind of cost us, and we’ve paid for it.”

Aleksander Barkov’s four-on-three power-play goal at 4:43 of the third period — Islanders defenseman Adam Pelech lost the puck at the opposing blue line with the teams skating four-on- four and was called for interference as he tried to recover — gave the Panthers a 3-2 lead. Troy Brouwer added an empty-netter.

The Islanders again struggled in the second period, as they did in Thursday’s 4-2 loss to the Lightning, though Brock Nelson’s team-high eighth goal did give them a 2-1 lead at 8:10.

But the Panthers tied the score at 2 with 45.1 seconds left in the second period. The Islanders iced the puck and lost the defensive zone faceoff, and Mike Hoffman — who scored the overtime winner in the Panthers’ 3-2 comeback win at Barclays Center on Oct. 24 — banked in a shot off Pulock’s left skate.

“The next game is big because we want to stop it now and keep going the way we were playing when we were winning five straight games,” Nelson said of Tuesday’s game against the Canucks at Barclays Center.

The lack of power-play success is starting to sap momentum during games.

“If you have a lot of them and if it doesn’t go very well, you lose a little bit of momentum,” Islanders coach Barry Trotz said. “We’ve got to get that right. We’re getting two five-on-five goals each night. If we get another one and get to three, we’re going to win some games.”

Barzal had tied the score at 1 by lifting a backhander past Luongo after Lee sprung him at the opposing blue line for a breakaway.

The 21-year-old won the Calder Trophy as the NHL’s rookie of the year with 22 goals and 63 assists. He has two goals and 12 assists as a sophomore.

On Saturday, he was moved between top-line wings Lee and Josh Bailey, the spot former captain John Tavares vacated when he signed a seven-year, $77-million deal with the Maple Leafs.

“It’s just been a fun ride the last year and a bit,” Barzal said. “It went by quick. There’s ups and downs being the first 100 games, getting used to the speed and the size of these guys up here. I’m just trying to adapt and keep playing my game.”

Notes & quotes: Defenseman Luca Sbisa and left wing Ross Johnston remained the healthy scratches . . . Left wing Matt Martin (upper body/day to day) missed his fourth straight game.

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