NEW YORK -- Matt Niskanen is known for being a shutdown defenseman.

On Tuesday, his offense was impossible to stop and it was so effective that the Washington Capitals were trying to get Niskanen a third goal.

Niskanen scored his first two goals of the season at the start and end of the third period as the Capitals extended their winning streak to five games with a 4-2 victory over the New York Islanders.

"It's good," Washington coach Barry Trotz said. "Matt is known more for his shutdown role. Anytime you get a couple of goals, I think that's a feather in his play. And the guys were excited, they were trying to get him the third one."

The third one never came but the two Niskanen scored were good enough.

Niskanen had plenty of room parked alone in the right faceoff circle to put a wrist shot past Jaroslav Halak at 1:58 of the third period shortly after a Brock Nelson turnover behind the net. That play ended a 43-game regular-season drought that dated to March 5, when he scored an overtime goal at Boston.

"It feels good," Niskanen said after scoring the 45th and 46th regular-season goals of his 11-year career. "It's nice to see the puck go in. That first one may be the best chance I had all year. So I'm glad that one went in at least."

The first goal stood as the game-winner and marked the fourth straight time Niskanen had the game-winning goal. He also scored tiebreaking goals in the third period March 2 against Toronto and Feb. 7 against Philadelphia.

"I did not know that," Niskanen said. "I'm scoring at the right time, but when they do they mean something."

With 1:58 remaining, Niskanen finished it off with a power-play tally, putting a slap shot past Halak. It gave him two goals for the second time in his career.

The other instance time since March 4, 2014 for Pittsburgh against Nashville when he was set up by Evgeni Malkin and Sidney Crosby.

"His first goal was phenomenal and the last one was a nice screen," Washington goaltender Braden Holtby said. "He plays so solid every night, offensively, defensively -- it's fun to play behind him."

Brett Connolly and Justin Williams scored second-period goals for the Capitals, who are 5-0-1 in their last six games since a 3-0 home loss to New York on Dec. 1.

Holtby made Niskanen's game-winner stand by making 12 of his 26 saves in the third. He kept the lead by lunging forward in the crease to make a glove stop on Josh Bailey's backhand attempt with about 11 minutes left and then by getting his glove on an attempt by John Tavares two minutes later.

Nelson and Nikolay Kulemin scored for the Islanders, who are 5-2-1 in their last eight games but allowed two power-play goals for the first time since Nov. 1 and had 15 giveaways.

"I don't know if it's effort," New York coach Jack Capuano said. "To me, tonightthe third goal was structural. You had five guys on one side of the ice, so that's a mistake. I'm just talking about confidence and poise.

"You can work. Some guys are working, some guys are working smart but at the same time when you work, there's got to be a method about how you go about your business."

Halak, who had a 38-save shutout in Washington on Dec. 1, allowed four goals for the sixth time this season.

Nelson opened the scoring at 9:32 of the opening period by inching past Washington defenseman John Carlson and firing a wrist shot from the right circle that sailed above Holtby's glove.

Washington tied the game at 2:09 of the second when Lars Eller flew past Islanders defenseman Johnny Boychuk on the left wing and slid a pass to Connolly, who slipped the puck through Halak's pads from near the crease.

The Capitals took a 2-1 lead about 5 1/2 minutes later on a power play when Williams tipped rookie Jakub Vrana's shot past Halak.

New York tied it at 10:41 moments after Casey Cizikas shot wide of the net. Cizikas regained possession near the right faceoff circle and made a nice pass to defenseman Nick Leddy, whose slap shot from the right point deflected off Kulemin and eluded Holtby.

NOTES: Washington LW Andre Burakovsky was a healthy scratch for the first time this season. Burakovsky scored twice in the season opener at Pittsburgh on Oct. 13 and has not scored since, though he has eight assists. Coach Barry Trotz described scratching Burakovsky as a "reset", saying: "It's been playing on his mind, a little bit, trying to get some production and what have you, and his ice time has gone down. I said 'just get a reset.'" ... New York returned D Scott Mayfield to Bridgeport of the AHL. Last Tuesday, Mayfield scored the first goal in a 4-2 win over the New York Rangers. ... C Alan Quine was a healthy scratch for the Islanders and D Adam Pelech (upper body) missed his seventh straight game. . ... New York C Casey Cizikas was cut by skate blade early in the first period but only missed a few shifts getting stitches and played 11 minutes.