WASHINGTON - An injury to Steve Mason - who has been playing as well as any NHL goalie recently - overshadowed the Flyers' gritty 3-1 win over the Washington Capitals Sunday at the Verizon Center.

Mason will be out indefinitely with an undisclosed injury and will be examined by a doctor in Philadelphia on Monday. He did not accompany the team to Montreal and probably won't join the Flyers in any of the three remaining games on the trip, general manager Ron Hextall said.

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"He won't be coming to Montreal, so I guess it's that serious," Hextall said of Mason's condition.

"It was a tough moment, losing Steve," said defenseman Mark Streit, who scored the Flyers' first goal. "But Razor [Ray Emery] came in and made some key saves."

The Flyers took a 2-1 lead when Wayne Simmonds took a deft pass from Sean Couturier and scored on a left-circle wrist shot about four minutes into the third period. It was Simmonds' 19th goal, tops on the team.

The Flyers allowed a season-low 14 shots; it was Washington's lowest shot total since 2011.

"That's about as good as you can play defensively," said Emery, who relieved Mason with 8:42 left in the second period, stopped five of six shots, and registered the win. "We really took everything away from them."

After the game, Hextall would say only that Mason had a lower-body injury and that he didn't think it was related to the right-knee problem that sidelined the goalie last month for six games.

Hextall said the Flyers would recall Anthony Stolarz, 21, from the Phantoms. Rob Zepp would have been the first choice, but he injured his right leg Saturday.

The win, iced on Jake Voracek's empty-net goal, gave the Flyers a six-game points streak (5-0-1).

The Flyers outshot the Capitals, 25-14, even though Washington had six power plays to the visitors' one.

"Everybody worked really hard, and the defense had really good gaps," Streit said. "We didn't give them a whole lot of time and space, and our forwards came back really hard as well. Certainly one of our better games this year."

Mason limped off the ice and was carried to the dressing room with the Flyers holding a 1-0 lead.

"You don't want to see Mase go down, but I've gone in a few times before," Emery said. "Just go in there and work hard."

In his last eight appearances, Mason has a 1.17 goals-against average and a .961 save percentage. He entered the day tied for fourth in the NHL in save percentage (.925) among goalies with at least 1,300 minutes.

Mason, 26, was playing in his fifth game since returning from an injured right knee. He missed four games earlier in the season with a back injury.

About two minutes after Emery replaced Mason, Alex Ovechkin scored a power-play goal from in front on the second shot the backup goalie faced. The shot tied the score at 1 with 6:31 to go in the second period.

Other than Ovechkin's goal, the Flyers' penalty kill was flawless. The Caps had just three shots in 10:11 of power-play time.

All told, Washington had five shots in the first period, five in the second, and four in the third.

The Flyers "had a little more jump today; they looked fresher than us," said Caps coach Barry Trotz, whose team had its three-game winning streak snapped.

The Flyers outworked the Caps throughout the game.

"It's a tough building to play in, it's an afternoon game, and Mase gets hurt," Emery said. "It's an opportunity to have some mental collapses, but it was our most solid game of the year, I thought."