Nolan Patrick missed Wednesday’s game with a head injury. Jake Voracek was sidelined, again, by some sort of lower-body ailment.

Without those two key forwards, the Flyers figured to be overmatched against the defending Stanley Cup champion Washington Capitals.

And they were -- at least for the first 40 minutes.

Washington built a 5-0 second-period lead and then held off a furious rally as it defeated the shorthanded Flyers, 5-3, at the Wells Fargo Center.

“We weren’t jumping on pucks. We weren’t making good reads in the D zone,” defenseman Andrew MacDonald said. “It just seemed like we were a step behind in the first two periods. It took us a while to figure it out, and by the time we did, it was too late."

Goalie Brian Elliott, who had compiled a 2.28 goals-against average and .936 save percentage in his previous six outings, allowed four goals on 19 shots and was removed from the game with 15 minutes, 32 seconds left in the second period.

The Caps won their fifth straight, while the Flyers suffered their first regulation loss in six games (4-1-1). The Flyers are seven points out of a playoff spot with 15 games left.

In other words, their playoff hopes are hanging by a thread despite a 16-4-2 run.

“Obviously, there’s minimal room for error at this point for us,” MacDonald said. “Luckily, we still have games to look forward to, and they’re important games.”

Washington goalie Braden Holtby (27 saves) became the second-fastest goalie in NHL history to register his 250th win, doing it in 409 games. Ken Dryden, who played in an era when teams didn’t have a chance to turn ties into wins in overtime or a shootout, reached the mark in 381 games.

It was the first of three meetings between the teams in a 10-game span for the Flyers.

Washington set the tone by building a 2-0 lead and outshooting the Flyers, 15-7, in the opening period.

“The way we played in the first two periods, that can’t happen in a big game like this. They outworked us ... .but we just have to build off the third period,” said Phil Myers. The rookie defenseman collected his first NHL goal, scoring from the high slot after taking a drop pass from Claude Giroux (two points) with 11.3 seconds left in a Washington-dominated second period.

Myers’ punched the air repeatedly after the goal, which cut the Caps’ lead to 5-1.

Ten seconds into the third period, Giroux made it 5-2. Scott Laughton deflected MacDonald’s point drive past Holtby to cut the deficit to 5-3 with 12:12 remaining. Holtby later made key stops on MacDonald and James van Riemsdyk as the Flyers’ amped up their attack.

Alex Ovechkin is known for his scoring prowess, but the big left winger set up the game’s first goal with a deft pass. Falling to one knee, he whipped a feed to Tom Wilson, who scored from the slot with 14:05 to go in the first.

With 5:44 remaining in the first, Brett Connolly’s left-circle shot went off Elliott’s glove and caromed into the net, increasing the lead to 2-0. The goal wasn’t awarded until a stoppage in play and a video review, which showed the puck had bounced off a camera inside the net – and not the crossbar.

The Capitals then scored three goals in a 3:10 span early in the second period to build a 5-0 lead.

“They were skating, making plays and walking right through us, and we watched them play,” Laughton said.

While the Caps were on a power play, Ovechkin (league-high 46th goal) fired a shot through Elliott’s legs to make it 3-0 with 17:28 left in the second. Less than two minutes later, Andre Burakovsky beat a shaky Elliott to the short side from the left circle, putting the Flyers in a 4-0 hole.

Exit Elliott. Enter Cam Talbot.

“It’s disappointing, but we’ll move on,” Elliott said.

Nicklas Backstrom, left all alone in front as he took a behind-the-net- pass from Jakub Vrana, scored on the first shot Talbot faced, and the Capitals were coasting at 5-0.

Without Patrick and Voracek, Flyers interim coach Scott Gordon used about a gazillion line combinations. Not much clicked until the third period.

“We weren’t moving our feet or doing the things that made us successful in Long Island,” Laughton said, referring to Sunday’s 4-1 win.