Karl Alzner and his Washington teammates celebrate one of four goals scored in a stretch of the third period. (Katherine Frey/The Washington Post)

It was 2:45 p.m. when the Washington Capitals seemingly woke up for Sunday’s matinee against the Philadelphia Flyers. After stumbling through the first two periods, Washington suddenly returned to its dominant form of late, scoring four goals in the first seven minutes of the third period to add another blowout to its winning streak.

This one was a 5-0 rout of the Flyers to lift the Capitals to a ninth straight win and the league’s best record, with 63 points. In the past six games, all against teams in playoff position, Washington has scored 23 more goals than the competition.

The Capitals insisted they haven’t stepped back to appreciate the ways in which they have crushed quality competition lately. There was that 5-0 win over the Blue Jackets when Columbus came to Verizon Center with a 16-game winning streak. The Atlantic Division-leading Montreal Canadiens lost, 4-1, to Washington at Bell Centre. The Pittsburgh Penguins were shut out for two periods by the Capitals before losing, 5-2, and the Chicago Blackhawks, one of the Western Conference’s top teams, were shellacked by a 6-0 score.

“We haven’t talked about it a ton,” defenseman Matt Niskanen said. “It’s been fun, though. I think guys are enjoying coming to the rink right now. We’re kind of in this every-other-day-play-a-game-type schedule right now, and I think that’s where we play our best. Guys are enjoying that. We’re getting some offense, but we’re also getting some shutouts mixed in there, too, so that’s a good sign. We’re playing really good hockey — still room to grow, I think, in the long term — but it’s pretty fun right now.”

On Sunday afternoon, backup goaltender Philipp Grubauer got his second shutout of the season, making 24 saves, and gave the team its fourth shutout in its past six games. The Capitals haven’t allowed an even-strength goal since Jan. 3.

Capitals center Nicklas Backstrom skates between Philadelphia Flyers defensemen Andrew MacDonald, left, and Ivan Provorov in the third period. (Katherine Frey/The Washington Post)

[John Carlson leaves game against Flyers with lower-body injury]

Andre Burakovsky got Washington on the board in the second period, and then the team poured it on in the third, when Justin Williams and Niskanen each scored twice.

“Everybody seems to be doing their job at a high level right now, and that’s why we’re being successful,” Williams said. “When there’s a breakdown, someone’s there to help you out, and when there’s a total breakdown, our goaltenders are there to shut the door. Not a great start but a great finish.”

Washington had just 10 shots on goal through two periods, its lowest 40-minute shot total of the season. But the Capitals still held a 1-0 lead entering the third after Burakovsky’s power-play goal. Flyers defenseman Michael Del Zotto fanned on an attempt to clear the puck out of the Philadelphia zone, and Bura­kovsky pounced on the turnover and unfurled a shot from the slot.

“I think from the past, we’ve been a little bit slow when we have an early game,” Burakovsky said. “I think it showed a lot in the first period today. Maybe we just woke up from a nap or whatever in the second and third. I think we finished off with a really good game here.”

After the Capitals’ power play fell into an early-January slump, it has warmed up recently, with four goals in the past four games. But Coach Barry Trotz warned that Washington would need to be wary of the Flyers’ fourth-ranked power play, hopeful his team would have discipline. The Capitals took five minor penalties, but the team’s penalty kill and Grubauer withstood nine shots on goal in shorthanded situations.

As the Capitals failed to sustain any offense in the first 40 minutes, Grubauer had some close calls. The Flyers had just four shots on goal in the second period, but they had two near-goals. Grubauer uncharacteristically let in a Radko Gudas shot from the red line, but the play had been whistled dead for offside just before. On a power play, a Mark Streit shot went off Grubauer and then off the post.

“We had some good fortune,” Trotz said. “They hit a post, and they delivered one from the red line that was close. I mean, when we weren’t — maybe not struggling, but when we weren’t scoring [earlier in the season], a lot of those pucks weren’t going in. Right now, they’re sort of going in our favor. They all even out. We always talk about, that during the course of a year when you’re getting chances and not having success, if you stay with it, you’ll have some success.”

That bought time for the Capitals to ignite in the third period. They have been playing like the league’s best team recently, and with their win against Philadelphia on Sunday, that became official.

“We don’t care about the winning streak right now,” Capitals center Nicklas Backstrom said. “We would like to win every game, and right now we’re playing good hockey, but we’re not thinking about a winning streak. We’re just trying to get ready for next game and see how it goes.”