WASHINGTON -- The Washington Capitals' penchant for slow starts often have left them digging out of an early hole, but at this point, it's almost become second nature for the NHL's best team to kick into high gear once the second period rolls around. And when that happens, very few opponents have been able to slow them down.

Defenseman Matt Niskanen's power-play goal with 6:22 left in the third period capped a rally from a two-goal deficit as the Capitals edged the Pittsburgh Penguins 3-2 on Tuesday in a potential playoff preview.

"We just have to realize that sometimes you have to wear teams down before you can make those skilled offensive plays," Capitals right winger T.J. Oshie said. "You have to play a little simple early and things will open up later."

In a hard-fought contest, Pittsburgh center Evgeni Malkin drew a high sticking penalty with 7:15 left, and the Capitals immediately took advantage, putting pressure on Penguins rookie goalie Matthew Murray. Niskanen boomed one shot from the blue line that Murray fought off, and when Niskanen received the puck once again, he did not miss, scoring his fourth goal of the season.

"This is a little bit more my forte -- taking slap shot after slap shot, get a lucky bounce and it goes in," he said. "Nice timing, too."

Washington has scored at least one goal in 26 of its last 27 third periods, and for the Penguins, the Capitals' comeback put a damper on a game that started with so much promise.

"We had the momentum most of the first period and they definitely came out hard in the second and we kind of backed off more than we wanted to," said Murray, who finished with 34 saves. "We let them dictate the pace, which we can't do, especially with a team like that."

Pittsburgh struck first when Malkin took a perfect feed from winger Carl Hagelin and bested both sliding defenseman Dmitry Orlov and Holtby for his 24th goal of the season and a 1-0 lead 6:14 into the first period.

The Capitals allowed opponents to score first in eight of their last nine contests, and looked disjoined early on, to the frustration of coach Barry Trotz.

"The starts, I mean, we couldn't string two passes together today," he said. "We're going have to adjust our alarm clocks, or whatever."

Early in the second period, Penguins center Sidney Crosby drew the attention of several Capitals defenders after dishing to Olli Maatta, making it easy for the defenseman to find right winger Patric Hornqvist cutting through the slot unchecked. Hornqvist buried his fourth goal in three games, sliding a shot under Holtby's pad to give Pittsburgh a 2-0 advantage.

Just 39 seconds later, however, Washington center Mike Richards flipped an innocent looking shot on net, but a great screen by right winger Tom Wilson allowed the puck to sneak through Murray and cut the Capitals' deficit to 2-1.

"After that, they took over the game," Hornqvist said. "We can't give them momentum like we did. That's the bottom line."

Center Evgeny Kuznetsov scored his 20th goal of the season late in the second period for Washington to tie the score at 2-2 heading into the third and from there, Holtby took over, with a couple of fantastic saves in the third period, including snagging a desperation shot from Hagelin with 32.8 seconds left, to pick up his 40th victory over the season.

If the playoffs began today, these two teams would face each other in the opening round, and if Tuesday's contest is any indication, it would be an intense series.

"It was a really good hockey game," Penguins coach Mike Sullivan said. "It was a close game, there were scoring chances on both sides. This was two pretty good teams going at it."

NOTES: Tuesday marked the first of 16 games in March for Pittsburgh, only the ninth time in franchise history the Penguins will play 16 or more games in a calendar month. ... D Mike Weber made his Capitals debut on the third defensive pairing after being acquired in a Feb. 23 deal with Buffalo. Capitals LW Daniel Winnik, acquired from Toronto on Feb. 28, was a scratch. In addition to Winnik, Washington scratched D Taylor Chorney and C Michael Latta. ... G Matthew Murray registered his first start in net for the Penguins since Dec. 30. ... Pittsburgh scratched D Justin Schultz, D Steve Olesky and G Jeff Zatkoff.