Washington, DC (Sports Network) - Alexander Semin's power-play goal with 5:27 to play in the third period was the game-winner as the Washington Capitals staved off elimination with a 3-2 victory over the Philadelphia Flyers in Game 5 of their Eastern Conference quarterfinal from Verizon Center.

"Evidently, it was pretty important because one thing about the Flyers is they don't quit," said Capitals head coach Bruce Boudreau. "In the third period they came at us. It was a real mental third for us to have our young guys keep composure with the effort the Flyers were giving."

Nicklas Backstrom and Sergei Fedorov tallied for the Capitals, who trail the series three games to two and head back to Philadelphia for Game 6 on Monday.

Cristobal Huet made 30 saves for his second win of the postseason.

Vinny Prospal and Derian Hatcher hit the net for the Flyers, who got a pair of assists from Danny Briere. Martin Biron allowed three goals on 26 shots in defeat.

"Their season was on the line and they came out and came out us hard," said Flyers head coach John Stevens. "It's a lesson we learned that won't happen again. We have to come out and initiate. We did a lot of good things as the game progressed, but it was going their way the first half of the hockey game."

The Flyers head into the pivotal sixth game without a key player, as forward Mike Knuble suffered a hamstring injury while diving to block a shot in the second period and did not return. He is expected to be out for at least the final two games of the series.

Semin's man-advantage tally provided valuable insurance, giving the Capitals a 3-1 edge.

He curled with the puck at the left point, cut in with a defender on his back, and threaded a shot through a mass of bodies in front and past a totally screened Biron.

However, Hatcher picked up his first goal of the playoffs only 44 seconds later and the Flyers were back within one.

Biron went to the bench for an extra attacker with 1:03 to play, and Huet immediately came up huge on two chances from in close.

Washington defenseman Tom Poti then made the save of the game with five seconds left. Briere unloaded a slapshot from the left circle which might have beaten a slow-to-react Huet if left untouched. Poti, though, smothered the chance with the shaft of his stick and the puck slowed enough to skitter off the outside of the net.

"These guys came out hard tonight and they wanted it a little bit more than us early in the game," said Briere. "Ultimately, that's where it cost us because we were trailing the whole game."

The Flyers buzzed around Huet on an early power play without a goal, then the Caps were awarded a two-man advantage shortly thereafter.

Semin, stationed in the left circle, found a seam through two defenders and hit Backstrom waiting at the right side of the crease for a slam dunk and a 1-0 lead at 7:31.

Biron continued to stand tall on the back half of the power play, and stopped 11 shots through the first period to keep his club down by just one.

"We wanted to have a good first period and that's what we did," said Huet. "We outshot them 12-4 and then we had that goal and we carried that over into the second."

Fedorov's backhander from the slot gave Washington a 2-0 edge 1:25 into the second, but the Flyers struck back with 7:25 to go in the period on their own 5-on-3 marker.

Briere held in the left circle and dished across to Prospal, who held a second to settle the puck before rifling it over a diving Huet. Philly failed to convert the second half of the power play but were on more solid footing down a goal after two periods.