Capitals goaltender Pheonix Copley took the loss against the Blues, his former team. (Ricky Carioti/The Washington Post)

At the sight of another flash of red behind the Washington Capitals’ net — the goal light sparking on again — the organist at Capital One Arena played an appropriately gloomy tune and fans started toward the exits Monday night. St. Louis Blues forward Vladimir Tarasenko had just scored on a power play to make it a three-goal game, and any hope of a Washington comeback was extinguished.

The fans didn’t have much reason to stay, and some who did booed the Capitals as they left the ice after a 4-1 loss. Washington was outshot and out-hustled by an opponent with a significantly inferior record, and the Capitals have now dropped two straight games and five of their past eight. More concerning is that the Capitals have looked lackluster for long stretches of games lately, perhaps not surprising halfway through the long season. Their lead in the Metropolitan Division has been trimmed to two points.

“We just didn’t seem as desperate as they did for some reason,” said defenseman Brooks Orpik, who skated in his 1,000th game. “Kind of seemed like we were second to the puck on a lot of loose pucks. A couple weird bounces there on two of the goals, but they were playing in our zone for the most part there in the second period. There were lucky bounces, but they were carrying the play for the most part. It was frustrating. . . .

“Sometimes you play well and you don’t get points, but that hasn’t been the case. We’ve been flat for the most part.”

Second periods have been Washington’s best this season — coming into this matchup with St. Louis, the Capitals had outscored opponents 62-42 in the frame — but after the Capitals were fortunate to get to the first intermission with a 1-0 lead on captain Alex Ovechkin’s power-play goal, they found themselves trailing 3-1 just eight minutes later.

With this being the first game of a back-to-back set — Washington will play at Nashville on Tuesday night — Coach Todd Reirden started Pheonix Copley against St. Louis, Copley’s former team. While the Capitals signed Copley as an undrafted free agent in 2014, he was part of the trade with the Blues that brought forward T.J. Oshie to Washington. And then when Washington acquired defenseman Kevin Shattenkirk from St. Louis in 2017, Copley was shipped back to the Capitals as part of that deal.

The organization liked Copley enough to acquire him twice, and this season, his first full one in the NHL, has been validation of that. Before Monday’s game, Copley had won 10 of 14 starts. But 3:18 into the second period, St. Louis center Ivan Barbashev scored from behind the goal line, wedging the puck past Copley, who hadn’t totally sealed the right post.

There wasn’t much Copley could do on the Blues’ next three goals. Less than two minutes after Barbashev scored, Vince Dunn’s shot from the point deflected off Washington’s Dmitry Orlov and Nicklas Backstrom before caroming into the net. Then, eight minutes into the period, Dunn corralled a puck along the wall and fed forward David Perron, who was left all alone in front of the net. Perron extended his point streak to 11 games with St. Louis’s third goal in less than five minutes.

“We didn’t play the right way. We didn’t play well, and you can see the result,” Ovechkin said. “All of us. It was bad play, bad game.”

With Ovechkin sent to the box to serve a delay-of-game penalty 9:26 into the third period, Tarasenko scored 58 seconds into the man-advantage to put the game all but out of reach. Washington finished with 29 shots to St. Louis’s 37, and for a second straight game the Capitals couldn’t score five-on-five.

“Obviously not good enough from our side,” Backstrom said. “We all know in here that we have to be better, especially five-on-five. Over the course of 82 games, you’re going to have your ups and downs, and hopefully this is our down. If you’re going to get better, I think we have to work a little harder, work better together, I think, and [better] than we have been the last couple of games.”

The previous time the Capitals played the Blues, just 11 days earlier in St. Louis, Washington players acknowledged that the opposition wanted the win more. And while the Capitals have maintained their place atop their division, that has been a theme of late. Defending champions have struggled the following season, but Washington’s lull might have come in the middle of this campaign.

“You can’t win every game, but with that kind of game, you can’t hope [the goaltender is] going to make a save or you’re going to have a power play or a lucky bounce,” Ovechkin said. “You have to work for it, and you’re going to get rewarded.”