WASHINGTON — With a sputtering offense most of this season, the Islanders have needed one of their goaltenders to steal a game or two.

Enter Jaroslav Halak on Thursday night.

With his team having flown in and gotten to its hotel here well after 2 a.m. following Wednesday night’s win over the Penguins at Barclays Center, Halak — who flew ahead of the team earlier Wednesday — stepped into the spotlight.

His 38 saves clamped down on the Capitals and Halak’s teammates produced three goals in a 4:28 span early in the third period for a 3-0 Islanders win, their season-high third straight.

“Our goaltenders need to play big,” Jack Capuano said. “Earlier in the year they were struggling, and if you look around the league, the teams that are winning are getting real good goaltending. Overall tonight, I thought we played real well and Jaro made some big saves.”

Halak stopped all 22 shots in the first 40 minutes of a scoreless game and had a bit of clock luck on his side.

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As the seconds wound down in the first period, Justin Williams appeared to beat the horn with a tap-in off the rush, but a review showed the clock hitting all zeroes just a moment before the puck fully crossed the line.

The Islanders started to wilt a bit after taking too many penalties and giving Alex Ovechkin and his pals lots of chances, none more so than in the opening minutes of the third, when Johnny Boychuk took a delay-of-game minor to give the Capitals their fifth power play of the night.

Ovechkin uncorked three of his patented off-wing blasts during that advantage. One hit the post and Halak, moving well and playing aggressively, stopped the other two.

Soon after that power play ended, Casey Cizikas got past Dmitri Orlov and sprung Shane Prince on a breakaway, and his quick wrister beat Braden Holtby to open the scoring at 3:15.

By the 7:43 mark, the Islanders were ahead by three for the second straight night.

Josh Bailey and John Tavares created a couple of chances in tight. Brock Nelson, just off the bench, raced on to the puck and slammed it through Holtby and two Capitals defenders for a 2-0 lead.

A minute after that, Andrew Ladd fed Jason Chimera, who shelved a backhand on the rush and sent a healthy portion of the Verizon Center customers to the exits.

“It’s amazing. Some games we get so many chances, like last night, and there’s posts, pucks laying in the crease that don’t go over the line,” said Prince, who hit two posts on Wednesday night. “We took advantage of our opportunities tonight and Jaro shut the door.”

Wednesday night’s blown 3-0 lead and pulled-out-of-the-fire 5-3 win over the Penguins gave the Islanders some confidence, though Thursday night’s starting goaltender missed all the fuss.

“I went to sleep after the second,” Halak said. “I wanted to get a good rest.”

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He didn’t miss his team finally producing a few goals for him — Thursday night was the first time in his last six starts that the Islanders scored more than two — and Halak did the rest for his 40th career shutout and the Isles’ first of the season.

“We won three in a row, but there’s still some things to be cleaned up,” Halak said. “Still, it’s a good feeling.”