The Pittsburgh Penguins celebrate after a second-period goal in their 4-3 OT victory over the Washington Capitals in Game 6. (Toni L. Sandys/The Washington Post)

Braden Holtby stayed on his stomach, sprawled in front of his net, face down to the ice. He got up, skated to the bench and briefly buried his head in his hands.

The Washington Capitals had climbed out of a three-goal deficit to force overtime in a fight to extend their season. But this is why it’s called sudden death — Pittsburgh Penguins center Nick Bonino poked a rebound past Holtby in the extra period, handing the Capitals a 4-3 overtime loss in Game 6 that ended the Capitals’ campaign in the second round of the Stanley Cup playoffs.

The three-goal rally was a testament to a resiliency this team has shown all season, but “there’s no silver linings when you lose,” defenseman Matt Niskanen said. It also underscored a recurring theme for the Capitals, that they often saved their best for dire situations. That’s what put them in a 3-0 hole in the game and also a 3-1 series deficit. Both were too much to overcome.

But the legacy of this Capitals team will be another regular season heavyweight that again failed to reach the conference finals. The playoffs are said to be a second season, and the Capitals’ history here is a painful one — with a fresh new chapter.

“We’ve made some progress, but obviously, not enough,” Washington Coach Barry Trotz said. “We need to get through this round. That’s part of the deal.”

“Again we lost in the second round,” captain Alex Ovechkin said softly.

“Sucks,” he then muttered, almost to himself.

Whatever momentum the Capitals had from their furious rally to force overtime seemed to disappear in the extra period. They were reeling, outshot 7-3 after Bonino ended it 6 minutes 32 seconds in. Holtby stopped the first shot from Carl Hagelin, but the rebound squirted off his pad and Bonino was there all alone, punching in the loose puck and setting off a wild celebration on the Consol Energy Center ice.

“There’s a lot of ‘What ifs?’” Holtby said. “But the biggest thing is we just didn’t do enough little things to win a series.”

It looked like it was over earlier. The Capitals leaned forward on the bench, their forearms resting on the boards as they watched and waited — and then waited some more. It seemed like they’d have to keep waiting until next season, the Penguins’ 3-0 lead through the first half of the game just too much.

But with a blast in the third period, that bench leaped up, the team’s arms raised. That comeback the Capitals seemed to expect would come eventually did. John Carlson’s shot on the power play tied the score at 3 with 6:59 left. Of all the ways for Washington to erase that deficit, it took three straight delay of game penalties for this Carlson goal to happen.

The penalties for sending the puck over the glass came within a span of just more than two minutes. Chris Kunitz’s gave the Capitals a power play 10:32 into the third period. Bonino was then whistled for the same infraction 66 seconds later, giving Washington a five-on-three for 54 seconds. Two seconds after Kunitz’s penalty was killed, Ian Cole then improbably went to the penalty box for the same thing.

On the second five-on-three, the Capitals’ power-play wrinkle of Carlson and Ovechkin swapping spots, with Carlson moving to the left faceoff circle, paid off. Carlson wildly fist-pumped, momentum squarely in Washington’s favor after Pittsburgh seemed poised for a comfortable win. That goal set the stage for overtime.

“I think we could’ve had a little more killer instinct,” Carlson said.

The Capitals’ comeback had also started with a power play. With Washington down 3-0 in the second period, Kunitz was called for tripping Marcus Johansson, and T.J. Oshie snapped in a pass from Nicklas Backstrom to get the Capitals on the board with 1:30 left in the period and give them some hope going into the second intermission.

Oshie and Justin Williams were Washington’s two splashy offseason acquisitions, the two forwards that made the Capitals trendy Stanley Cup favorites. Fittingly, they were the ones who helped jump-start this Washington rally on Tuesday. Known for a career of clutch playoff performances, Williams scored on a wrister 7:23 into the third period.

“Too little, too late,” Williams said after the game. The Penguins’ power play had capitalized with two goals on a high-sticking double minor by Brooks Orpik. Earlier in the series, it was Orpik’s high, late and illegal hit on Pittsburgh’s Olli Maatta that forced the Capitals to play without him for three games after he was suspended by the league. Washington lost two of those games, falling into the 3-1 series deficit.

On Tuesday night, the Capitals had to play without Karl Alzner for most of the game after he was hurt halfway through the first period, and aside from taking two shifts to start the second period, he didn’t return. Trotz said Alzner has been “hurt for a while.” That Washington had taxed its other five defensemen for most of the game was evident in the overtime.

“If you ask most guys on our team, if there’s one guy we can’t lose, it’s him,” Holtby said.

Before the postseason started, General Manager Brian MacLellan said “we’re here to win a championship; anything less than that is unsuccessful.” His offseason moves — and his in-season ones — were designed to make this Capitals team better equipped for the postseason.

A trade for Oshie added a stable first-line right wing complement to Ovechkin. The signing of Williams and then later Mike Richards brought Stanley Cup winners into the dressing room, leadership for April, May and hopefully June. The acquisition of Mike Weber was supposed to provide defensive depth the team might need in a long playoff run.

Those moves were successful in the sense that Washington won a Presidents’ Trophy, the best regular season team. And while MacLellan and the team considered anything less than hoisting a Stanley Cup unsuccessful, the consistent dominance of these Capitals seemed to at least project something greater than just another second-round exit in the postseason.

“I wish we could have a victory in this round, and then we’d put that to bed,” Trotz said. “But we didn’t.”