J.T. Miller #10 of the Tampa Bay Lightning skates with...

J.T. Miller #10 of the Tampa Bay Lightning skates with the puck during the first period against Thomas Hickey #14 of the Islanders at Barclays Center on Thursday, Mar. 22, 2018 i Credit: Jim McIsaac

They are predictably unpredictable.

Or is it just consistently inconsistent?

Either way, the Islanders, nearing elimination from playoff contention, lost to the Eastern Conference-leading Lightning, 7-6, on Thursday night at Barclays Center in what could best be described as a doozy.

The Islanders (31-33-10) trailed by two goals just 2:35 into the game, 4-1 on Brayden Point’s shorthanded goal at 2:43 of the second period and 7-3 heading into the third period.

But they made the third period one of their most exciting of the season. They scored three goals in the opening 4:36, the last two by Anthony Beauvillier, to pull within one.

“They’re not an easy team to play against,” Beauvillier said. “It just stinks to go away with that loss.”

The Islanders became the first team to allow at least six goals in at least 12 games during a season since the 2008-09 Maple Leafs.

“Obviously, we didn’t play a great game, especially defensively,” John Tavares said. “We came out hard in the third and gave ourselves a chance.”

Anders Lee also scored twice for the Islanders, including a power-play goal that opened the third-period scoring at 1:35. The Isles went 3-for-5 on the power play.

“It doesn’t matter who we’re playing,” said Lee, who has 38 goals to extend his career high. “We’re down 7-3, we know we can come back, and we did. Obviously, we’re short a goal, but it was a game in the end.”

Rookie defenseman Ryan Pulock had two power-play goals on two one-timers from the left circle, the second of which cut the Lightning’s lead to 4-2 at 3:20 of the second period. Pulock became the first Islanders rookie defenseman to score two power-play goals in a game.

Former Rangers Ryan McDonagh and J.T. Miller, dealt to Tampa Bay at the trade deadline, made their first return to New York, and Miller scored two goals.

The Lightning (51-19-4), which went 2-for-4 on the power play and got 35 saves from Andrei Vasilevskiy, went ahead 7-3 on Miller’s power-play goal at 18:20 of the second period.

“It was kind of weird coming in from Newark [airport], seeing the city,” Miller said.

He’ll face the Rangers at Madison Square Garden on March 30. “That’s really the game I’m looking forward to,” he said.

Christopher Gibson, who made 36 saves in Tuesday’s 4-1 win over the Penguins, was pulled after Mikhail Sergachev blasted a power-play shot from the blue line just under the crossbar at 11:22 of the second period to make it 6-3.

Notes & quotes: Josh Bailey had two assists to give him 51 for the season. Mathew Barzal has 56 assists, and the Islanders have two players with at least 50 for the first time since 1992-93 . . . The Islanders loaned defenseman Sebastian Aho, 22, to Bridgeport . . . Alan Quine (injured reserve/lower body) skated in the morning, his second straight day on the ice with his teammates after resuming practice on Wednesday. “As early as two, three days, he could get the go-ahead from trainers,” coach Doug Weight said.

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