WASHINGTON — Slowly but surely, the young Washington Capitals are getting the hang of playoff hockey. They're rattling the opponent with physical play and playing the right mind games with timely complaints about the officiating.

The Philadelphia Flyers can only hope it doesn't become too much of a habit.

The Capitals jumped to an early lead with just the right mix of brawn and skill, and the Flyers waited too long to respond today in Washington's 3-2 must-win Game 5 victory in the first-round playoff series.

"There's a big difference from the first three games to the last two," said first-round coach Bruce Boudreau, who, like many of his players, is getting his first taste of the NHL postseason. "I guess this is why they say playoff experience is so important. I never would've thought about it on this scale, never being here."

Nicklas Backstrom, Sergei Fedorov and Alexander Semin scored the goals _ one in each period _ Cristobal Huet made 30 saves, and league MVP candidate Alex Ovechkin helped make up for another frustrating offensive effort by depositing Jim Dowd headfirst into the Philadelphia bench for the highlight hip-check of the game.

The Capitals outshot the Flyers 12-4 in the first period, outhit them 22-9 in the period and took a 2-0 lead early in the second before holding off a determined rally. The victory forced a Game 6 in Philadelphia on Monday night.

"The pressure is on them now," Washington center Brooks Laich said.

Vaclav Prospal scored for the Flyers in the second period, and Derian Hatcher made things interesting when he scored with 4:43 remaining in the game _ less than a minute after Semin's power-play goal had given the Capitals a 3-1 lead.

"They really came at us hard," Flyers coach John Stevens said. "To me, that's a lesson we learned that won't happen again. We've got to come out and we've got to initiate."

The Flyers will have to make do for the rest of the series without right wing Mike Knuble, who sustained a partial tear of his left hamstring late in the second period when he stumbled to the ice in a moment of indecision over whether to try to block a shot. Knuble had two goals and three assists during the series, including the game-winning score in double overtime of Game 4.

"I just kind of caught my heel and went down awkwardly," Knuble said.

The Capitals, in the playoffs for the first time since 2003 with a build-from-the-ground-up team, showed their playoff naivety when they were dominated in the first three games of the series. They stole Game 1 with a third-period comeback, but their best game before Saturday was the marathon Game 4 loss, when they started to match the physical play of the Flyers.

They kept it up Saturday, committing two roughing penalties in the first minute.

"I find they're really starting to pick up their physical play," Philadelphia right wing Scottie Upshall said. "As far as I'm concerned they're getting in some pretty good shots after the whistle."

But it was the Flyers' own inability to stay out of the penalty box that hurt their comeback attempt in the third period. They had to kill three Capitals power plays, including a goaltender interference call on Upshall in which he appeared to be pushed into Huet. The Capitals had a similar call go against them in Game 4, after which Boudreau left no doubt of his unhappiness about that call and several others.

In Saturday's game, Washington had six power plays _ scoring on two of them _ to Philadelphia's two.

"There's an old saying, 'The squeaky wheel gets the grease," Stevens said. "There's no question, you get short-handed, and it ends up being the difference at the end of the game."

For the first time in the series, the Capitals held the lead after the opening 20 minutes. They went up 1-0 after Ovechkin, bearing down on the crease, drew a hooking penalty on Kimmo Timonen during a power play to give Washington a two-man advantage. Backstrom converted the 5-on-3 by waiting on the doorstep to deposit Semin's cross-ice pass.

Fedorov gave the Capitals a 2-0 lead early in the second with a backhander on a feed from Viktor Kozlov, who worked hard to win the puck in the corner.

The tide began to turn when Fedorov's holding penalty gave Philadelphia a 5-on-3 power play later in the second period. Prospal scored his third goal of the series on the final second of the two-man advantage.

The goal energized the Flyers, who played the stronger and better over the second half of the game. But with Scott Hartnell in the penalty box for hooking, Semin's power-play goal gave the Capitals a 3-1 lead with 5:27 remaining. Hatcher quickly made it a one-goal game, but the Flyers couldn't get the game-tying score.

The Capitals remain in the series despite the lack of productivity from Ovechkin, who scored 65 goals in the regular season but has only one _ the Game 1 winner _ in the playoffs. At least he had better chances Saturday, putting six shots on goal after having only 13 in the first four games combined.

"My goals are coming," Ovechkin said. "I don't care if I don't score and we win. If I play one minute in a game and we win the game it will be a good result."