PITTSBURGH -- The Pittsburgh Penguins extended their winning streak to 10 games Tuesday night and remained atop the Eastern Conference playoff race.

Defenseman Matt Niskanen scored the game-winning goal midway through the final period lifting the Penguins to a 2-1 victory over the Washington Capitals. Pittsburgh allowed one goal for the second consecutive game and has now allowed two goals in its past three games and six goals in its past six games.

"One thing when it's not going perfect every night you can always play good defense," said Niskanen.

The Capitals, meanwhile, have lost five of their seven and sitting 13th in the conference.

After killing off the final seconds of a Washington power play, the CONSOL Energy Center crowd reached a fever pitch as Penguins captain Sidney Crosby carried the puck to just inside the blue line and dished it to Cooke, fresh out of the penalty box. Cooke then passed to a trailing Niskanen, who wristed the puck from the right hash mark past goaltender Brandon Holtby's stick side at 11:58 of the third for the game-winning goal.

"(The power play) killed us and they got momentum and the crowd got into it and then they scored right away," Capitals captain Alex Ovechkin said.

Penguins goaltender Marc-Andre Fleury made 28 saves to earn the victory, while Holtby made 33 saves in defeat.

"(Fleury) was really solid in his net, he was challenged a few times and had some flurries and he was real strong," Penguins head coach Dan Bylsma said.

The game remained scoreless after one period, but both goaltenders had to be sharp. Fleury turned aside all 10 Capitals shots in the first, which included a point-blank pad save on Jason Chimera at the 7:45 mark. At the other end of the ice, Holtby turned away all 11 of Pittsburgh's first period shots, including two during an early Pittsburgh power play.

The Capitals cracked the scoreboard first while on the power play when Troy Brower's shot hit Niskanen and deflected right to the stick of Ovechkin who quickly slapped the deflected puck just inside the left post at 8:14 of the second for his 12th of the season.

The Penguins countered with a power-play goal of their own less than three minutes later when Paul Martin blasted a shot from the blue line over the right shoulder of Holtby to tie the game at 1-1. The play actually resulted from a fanned shot attempt by Beau Bennett. He had the puck on his stick near the bottom of the right faceoff circle, but whiffed on the shot, allowing Washington defenseman John Carlson to poke the puck away. The only problem was that he poked it right to Crosby who slid the puck back to Martin for the one-timer.

The Capitals had a golden opportunity to take the lead midway through the third period when Matt Cooke took a two-minute boarding call and then an additional two minute unsportsmanlike conduct penalty.

The Penguins managed to kill off both penalties and then took the lead seconds later.

"When you run into a hot team like this they just seem to find a way to win," Washington forward Eric Fehr said. "I thought we deserved that one."

NOTES: Penguins forward Chris Kunitz led the NHL with a plus-24 entering Tuesday's game. ... Center Brooks Laich and defenseman Dmitry Orlov made their season debuts for the Capitals. ... The Penguins are the only team in the NHL without an overtime or shootout loss this season. ... The Capitals are the only team to not have participated in a shootout this season. ... Scratches for the Penguins were center Evgeni Malkin (upper body), defenseman Kris Letang (lower body) and defenseman Robert Bortuzzo. Scratched for the Capitals were right wing Joey Crabb, and left wings Wojtek Wolski and Aaron Volpatti. ... The Penguins next play Friday night at the New York Islanders. The Capitals next play Thursday night in Winnipeg to begin a unique back-to-back situation where they will play at the Jets on both Thursday and Friday night.