Capitals defenseman Kevin Shattenkirk is embraced by captain Alex Ovechkin after Shattenkirk’s overtime winner in Game 3 against the Penguins. (John McDonnell/The Washington Post)

On Monday morning, Washington Capitals defenseman Kevin Shattenkirk stood in front of his locker and admitted his struggles. Capitals Coach Barry Trotz had criticized his play this postseason, and Shattenkirk acknowledged that it had been poor.

“I think the most important thing for me to do is have fun, and I think that’s something I’ve lost along the way here,” Shattenkirk said before the night’s game.

Being at the center of a goal celebration after an overtime game-winner looked awfully fun. On a power play, Shattenkirk scored to lift the Capitals to a 3-2 win over the Pittsburgh Penguins in Game 3 of their Eastern Conference semifinal. That cut Pittsburgh’s lead in the series to 2-1, a deficit Washington surmounted in just the last round against Toronto.

But first, this roller coaster of a playoff game saw Pittsburgh’s best player get injured and the Capitals get out to a two-goal lead only to lose it in the last two minutes of regulation. The hero was the beleaguered Shattenkirk, traded to Washington in late February. Entering Monday night, he had a team-worst minus-seven rating in the postseason. Yet he was the one who helped extend the series to at least five games.

“Tonight was a great, great test for all of us,” Shattenkirk said. “There were a lot of different moments in the game where we had to see what we were made of.”

That started with the Capitals’ goaltender. Braden Holtby had been serenaded from the first minute of the game. Chants of “Holt-by” at PPG Paints Arena mocked the goalie, but for 58:07, his play mocked them back. He did his best impression of a wall, poised to guide the Capitals to a shutout.

But then with Pittsburgh’s goaltender pulled for an extra attacker, Evgeni Malkin’s goal halved Washington’s two-goal cushion with 1:53 left in the third period. The chants of “Holt-by” returned. Forty-eight seconds later, Justin Schultz scored from the point to tie the game and force overtime, a demoralizing circumstance after the Capitals had led since the first period.

But rather than feel defeated, Washington stayed positive going into overtime. Defenseman Trevor Daley was called for holding Marcus Johansson, and then Shattenkirk scored the game-winner on the power play.

“I think this room has a lot of character and a lot of maturity and the fact that, you know, we weren’t going to let that, the way that ended in regulation, affect the outcome of this game,” Holtby said. “I think it makes us go even harder if things don’t exactly go our way.”

The same can be said for Holtby. He had been yanked in Game 2 after allowing three goals on 14 shots through two periods. With his coach and teammates standing behind him as the starter for Game 3, Holtby was Washington’s best player most of the night, saving the first 26 shots he saw before Pittsburgh scored on two of its last three of regulation to force overtime.

The Penguins’ late surge was impressive considering their captain went down just 5:24 into the game. Sidney Crosby drove the net on a two-on-one, and Holtby was able to stop his scoring chance with a poke check. But in trying to stop Crosby, Alex Ovechkin made contact with the top of Crosby’s head with his stick, and Capitals defenseman Matt Niskanen then cross-checked Crosby high.

“It wasn’t intentional,” Niskanen said after the game. “I’ve seen the replay. In super slow-mo, it looks really bad. I caught him high. He’s coming across trying to score. As he’s doing that, he’s getting lower and lower, and when it’s happening that fast, you know, my stick and his head collided. I wasn’t extending trying to hit him in the head. It happened quickly.”

Crosby has a history of concussions, including one earlier this season, but it’s unclear whether he suffered a head injury or whether it was the way he landed awkwardly on his left leg that knocked him out of the game. Penguins Coach Mike Sullivan declined to comment on his status after game. He lay face down on the ice until a trainer helped him off. Crosby, who led the NHL with 44 goals during the regular season, did not return to the game. Forward Conor Sheary also went down in the second period after a collision with a teammate.

Niskanen was initially assessed a minor for cross-checking Crosby, but the penalty was then changed to a major and Niskanen was given a game misconduct. That put the Penguins on a five-minute power play, and it meant Washington would be down a defenseman for the rest of the game. Trotz opted to dress seven defensemen and 11 forwards to get Karl Alzner back in the lineup, so even with Niskanen out, Washington still had its usual complement of six defensemen.

A defining moment for the Capitals came when they were able to keep the Penguins off the board on the ensuing power play, which included two minutes of four-on-four after Malkin was called for closing his hand over the puck. In three minutes of power-play time, the Penguins tallied four shots on goal.

“Your best penalty killer is your goaltender, and I thought Braden was outstanding today,” Trotz said.

Shortly after surviving Pittsburgh’s power play, the Capitals got one of their own. Carl Hagelin was called for high-sticking, and then Bryan Rust sailed the puck over the glass to make it a two-man advantage. Just as the first penalty expired, Nicklas Backstrom banked in a goal off Pittsburgh defenseman Ian Cole. That gave Washington its first lead in the series.

That the Capitals were able to maintain their advantage for as long as they did was a testament to Holtby. The game took on a nasty, physical tone after Crosby’s injury, and while there was mayhem on the ice at times, Holtby looked poised in net. With Pittsburgh on the power play three times in the second period, Holtby made 15 saves in the frame. Evgeny Kuznetsov then added to the Capitals’ cushion with a third-period goal. It still wasn’t enough to avoid overtime.

But it was still the Capitals who left smiling, and it was Shattenkirk who’d had the most fun.

“Tonight felt like it was back in that groove,” Shattenkirk said.