Josh Bailey of the New York Islanders celebrates his third-period...

Josh Bailey of the New York Islanders celebrates his third-period goal against the Florida Panthers with his teammates at Barclays Center on Monday, March 14, 2016. Credit: Jim McIsaac

It was no overstatement to call the first 40 minutes of Monday night’s Islanders performance the worst two periods they’ve played all season.

They were down by two goals and had only 11 shots on Panthers goaltender Roberto Luongo. During the second intermission, their coach didn’t even enter the dressing room.

Said Jack Capuano, “I didn’t want to break anything.”

It was quiet in that room without the coach. “There wasn’t a whole lot said,” Kyle Okposo said after the Islanders’ 3-2 victory at Barclays Center. “To a man, we all knew the situation.”

And after 12-plus minutes of increased effort but no results, the Islanders found a solution.

Okposo wired one past Luongo at 12:50 of the third period to cut the deficit to a goal.

Josh Bailey tucked in a gift-wrapped loose puck at the side of the net at 14:11 to tie it.

And Cal Clutterbuck, who was the hero inside of 90 seconds in a tie game at Madison Square Garden eight days earlier, swept a backhand from an impossible angle off the far post and in with 99 seconds left.

That completed a ridiculous comeback and produced a victory that was as big as any the Isles have had this season.

They still needed Thomas Greiss to the last second. The new starting goaltender kept it 2-2 right after Bailey’s goal by stretching full out to stop Vincent Trocheck’s redirection with just under five minutes to go. Then Greiss made two saves in the final 10 seconds to preserve the win.

“Not the way you draw it up,” said Clutterbuck, who has four game-winners among his 13 goals. “The third period, that was good stuff. We got two points with a terrible start, and we move on.”

They were about ready to move out of third place in the Metropolitan Division with the way the first two periods went, especially with a game Tuesday night in Pittsburgh against a Penguins team that trails the Islanders by four points.

The sluggishness that defined Saturday’s opening period in Boston returned, with the light-footed Panthers beating the Islanders to every puck and keeping everything away from Luongo in the Islanders’ brief forays into the offensive zone.

Aleksander Barkov’s easy tap-in put the Panthers up after one. Nick Bjugstad’s po wer- play goal — the seventh the Islanders have allowed in their last 19 times shorthanded — put the visitors up by two and prompted some boos.

“We were flat,” Capuano said. “For some reason, and I have an idea, but some guys just aren’t there.”

Capuano jumbled his lines, as he’s done during midgame funks this season, and the switches generated some life.

Bailey, playing with Casey Cizikas and Brock Nelson, showed moxie, although it was John Tavares who set up the tying goal.

Then Clutterbuck, Nikolay Kulemin and Matt Martin outworked the Panthers below the faceoff circle to keep the play going until Clutterbuck’s fling to the net won it.

“This was a game we needed to win,” Okposo said. “Years past, even last year late in the season, I don’t think we find a way to win this game. I hope we’re maturing as a group.”

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