Brett Connolly checks the Penguins' Olli Maatta in the first period of Friday night’s 7-4 Capitals loss. (Gene J. Puskar/Associated Press)

It was fitting that this game, filled with free skates at the net and yawning pockets of space all over the ice, was decided by the Pittsburgh Penguins’ power play zipping the puck all over the offensive zone and, most importantly, into the goal behind Braden Holtby.

The Penguins’ second of three power-play goals, scored by Bryan Rust early in the third period, held up as the game-winner in their 7-4 win over the Washington Capitals on Friday night at PPG Paints Arena. The Capitals dug themselves a two-goal hole in the first period, then did so again in the opening minute of the second. They climbed out of that deficit but couldn’t scratch back after the Penguins scored four times in the third, including their final two power-play goals.

Capitals winger Alex Ovechkin notched two goals, and Evgeny Kuznetsov finished with a goal and an assist as the Capitals (30-16-5) had their Metropolitan Division lead trimmed to four points over the Penguins (29-21-3). The Penguins have scored 21 goals during their four-game winning streak, all at home.

“I don’t know. Too many to count, too many to remember,” Capitals defenseman Matt Niskanen said, shaking his head as he tried to explain the Penguins’ third-period burst. “Yeah, I don’t know. It’s just . . . penalties, self-inflicted wounds, can’t block a shot, bad defense all around.”

The Capitals’ penalty kill had not allowed a goal in three consecutive games heading into Friday, but the Penguins came in with the league’s top power play at 26.7 percent and the three players with the most power-play points in the NHL: Phil Kessel, Sidney Crosby and Evgeni Malkin.

“Don’t take any penalties; I mean, that’s plain and simple,” Capitals Coach Barry Trotz said Friday morning of how to slow the Penguins’ power play. His team ended up offering four five-on-four advantages. “If you want to nullify a real good power play, don’t let them go on the power play. That’s as simple as it can be.”

Penalties weren’t the Capitals’ problem early; taking care of the puck in the defensive zone was. Two turnovers led to two first-period goals for the Penguins, the second coming after rookie defenseman Christian Djoos gave it up right in front of the Capitals’ net. Hagelin intercepted Djoos’s pass, cut to his left and beat Holtby as Djoos slid by on his knees.

The game then took on a quick pace, and for fans swiveling their heads at center ice, it closely resembled a tennis match. The teams traded odd-man rushes, then traded a few more. Penguins goaltender Matt Murray stopped Chandler Stephenson on a breakaway. Holtby turned away a handful of close-range shots. By the end of the first period, the Penguins had 13 shots on goal, and the Capitals had 12.

The last of those Capitals chances was created by Ovechkin. The Capitals’ captain breezed past defenseman Kris Letang along the left wing, had his initial shot saved and then was credited with the goal when Pittsburgh defenseman Brian Dumoulin kicked the puck into his own net, slicing the Penguins’ lead in half. Ovechkin drifted backward toward the boards, raised both arms in the air and drove two fists toward his hips to celebrate his NHL-leading 31st goal.

The Penguins’ power play restored the two-goal lead — Patric Hornqvist scored off a feed from Crosby at the start of the second — before Capitals defenseman Dmitry Orlov scored on a slap shot that cut the lead in half again less than three minutes later. Eight minutes after that, the Capitals drew even when Kuznetsov buried a shot past Murray at the end of a broken play.

“It doesn’t matter for us, for me personally; it’s about the team winning, right?” said Kuznetsov, who scored for the first time in eight games. “We didn’t today. Of course you’ll look at the tape, look at what’s good and what’s bad.”

The bad, ultimately, was the first 10 minutes of the third period. Malkin nudged the Penguins back ahead 61 seconds into the period with a four-on-four goal, Ovechkin erased that lead with his 32nd goal less than a minute later, and then the Capitals’ penalty kill faltered twice more. The first of the Penguins’ final two power-play goals came off Rust’s stick to make it 5-4. And after Kessel scored less than two minutes later, Holtby headed to the bench as the home crowd chanted his name. Philipp Grubauer later gave up the Penguins’ seventh score, to Malkin on the power play, and Holtby glanced up at the video board on his way off the ice.

It showed a lot of goals, a lot of shots on net — and a deficit the Capitals could not overcome.

“At the end of the day, we just gave them a few too many odd-man rushes, and we lost the special teams war,” Trotz said. “We didn’t kill any [penalties] off, and we didn’t score any [on the power play], so that ends up being the difference — those three goals. We can play better. We can play better.”