Capitals defenseman Christian Djoos celebrates with Alex Ovechkin (8) after scoring during the second period against the Penguins. (Jonathan Newton/The Washington Post)

As Christian Djoos’s stat line flashed across the Capital One Arena videoboard and low cheers of his name echoed through the stands, the 23-year-old rookie looked up and gave a slight shake of his head as if still in disbelief. Beside him, Capitals defenseman John Carlson gave him a nudge of encouragement.

The Capitals lost Wednesday night, 3-2, to the Pittsburgh Penguins, sinking themselves by taking six penalties and then allowing three power-play goals. But at least one good thing may have come out of the loss: an answer for the team’s struggling third defense pairing. In his NHL debut, Djoos scored a goal and recorded an assist, shining brighter as the game went on and potentially carving out a role for himself in the lineup.

“First game in the NHL, and you get a goal and an assist,” Djoos said. “That wasn’t my plan really when I showed up at the rink. I was going to play good and play a structured game and detailed game, but happy with the goal and the assist. But couldn’t get the win, so not good enough.”

After Washington’s third defense pairing underwhelmed in the first three games of the season, barely seeing the ice late in an overtime loss to Tampa Bay on Monday, Coach Barry Trotz made a change to that duo before the team’s game against Pittsburgh. Trotz scratched veteran Taylor Chorney in favor of Djoos, the organization’s seventh-round pick in 2012. Djoos had made the opening-night roster out of training camp, but he was forced to watch the first three games rather than play in them.

On Wednesday night, Trotz opted to sporadically rotate the team’s top-four defensemen around Djoos and Aaron Ness rather than deploy an inexperienced third pairing against the Penguins. After Djoos played less than three minutes in the first period, his debut seemed to be going awry when he was called for tripping 6:26 into the second.

With goaltender Braden Holtby down across the crease, Pittsburgh’s Patric Hornqvist swatted a puck under his outstretched arm six seconds before the Penguins’ power play expired for a 2-0 lead. Djoos then had to take the skate of shame out of the penalty box.

But Djoos ultimately made up for the penalty. Just as the public address announcer declared a minute left in the period, Djoos slammed in a one-timer set up by Lars Eller to cut the deficit to 2-1.

“I thought he was awesome,” defenseman Matt Niskanen said of Djoos. “Lot of confidence. He wasn’t afraid, moved the puck really good out of the zone and then scored a first goal in his first game. That’s pretty unbelievable. It’s awesome. Those never get old.”

Before Washington could get to second intermission with the momentum from Djoos’s goal, forward Alex Chiasson was called for holding with 4.5 seconds left in the period. The Penguins were on the power play when the puck dropped for the third period, and for the third time in the game, Pittsburgh scored directly in front of the net on the man-advantage, Conor Sheary getting the credit this time.

Once again down by two goals, Nicklas Backstrom fed Djoos at the side of the net 12:59 into the third period, and Djoos stickhandled around Justin Schultz to pass the puck across the crease to a waiting Alex Ovechkin. Ovechkin tapped in his eighth goal of the season, raising his arms victoriously and then wrapping Djoos into his second goal celebration of the game.

“The thing with Christian is we know that he’s a good hockey player,” Trotz said. “He’s going to have to continue to get strong and continue to play at this level. You can see the instincts are really good. He’s got a real good sense for the game. His IQ is really good.”

That wasn’t enough to make up for the six minor penalties the Capitals took during the first two periods. Entering Wednesday night’s game, Washington’s penalty kill had allowed just one goal in 14 times shorthanded, and it was Tampa Bay’s overtime winner in a four-on-three on Monday night. The Penguins had the third-best power play in the league last year, and they made the Capitals pay for their penalties.

“We’ve got to stay out of the box,” Backstrom said. “It comes down to execution. We’re not executing our plays in the [defensive] zone and then they get to play in the offensive zone and they’re running around and, honestly, they’re really good at that. That’s when we take penalties. So we’ve got to start with execution and play a little simpler so we don’t take these penalties.”

The last time the Capitals played the Penguins in this building was five months ago, Game 7 of the Eastern Conference semifinals. Washington was shut out, 2-0, and Pittsburgh went on to a second straight Stanley Cup championship. That loss and how poorly the Capitals played for stretches in it lingered on the team’s mind through the offseason and into training camp. Meanwhile, the Penguins visited the White House on Tuesday as a celebration of their championship victory.

After all of that, the feelings going into this chapter of the bitter rivalry? “Just hatred,” Trotz said before the game. “You hate the guys that bumped you out.”

This game was never going to erase last season’s result, but it served as an early-season measuring stick for the Capitals. It revealed areas Washington still has to improve, like cutting down on penalties, and it also served as a coming-out party for a young defenseman.

“It’s a process,” Trotz said. “It’s one game and we’ll be patient. His first game was real good.”