The New York Islanders lost a playoff game last night the way they used to win one.

They took "bad" penalties, said center Bryan Trottier, including a five-minute high-sticking call midway through the third period. They wore themselves out killing them. Then, when overtime rolled around, that hallowed segment of Stanley Cup time in which the Islanders were 21-5 before last night, they were tired.

So they made mistakes that resulted in the first opening playoff loss in their history.

Washington right wing Alan Haworth's overtime walk-up goal won the first game of this Stanley Cup playoff series, 4-3, at Capital Centre.

But the Islanders, four-time Stanley Cup champions, actually started losing this game early. Haworth's shot 2 minutes and 28 seconds into overtime only finished an evening of frustrations.

They didn't just lose. They unraveled.

It began with three first-period penalties that forced the Islanders to go nearly 8 1/2 minutes before they took their first shot on Washington goalie Pat Riggin.

It ended when, during a series of spontaneous mistakes, the Islanders' defense broke and allowed Haworth to skate in untouched on goalie Bill Smith.

Three New York rookies -- Gord Dineen, Pat Flatley and Pat LaFontaine -- and one second-year player -- Paul Boutilier -- were on the ice when Haworth ended the game. The Islanders are known as a team of veterans. But most were watching the final scene from the bench.

Flatley and LaFontaine rushed toward Rod Langway at the point. Langway passed to Haworth when he saw them coming.

"The problem was, two of our players went to the point," said Islanders Coach Al Arbour. "They followed each other, and the guy (Haworth) walks in."

Dineen, meanwhile, was entwined with Lou Franceschetti in front of Smith.

"I should have broke away from Franceschetti at that point," Dineen said, referring to the moment Haworth started in. "I didn't really see him until he was at the top of the circle, and then it was too late."

Bob Bourne, the veteran left wing who just came back after missing nearly half the season because of a hand injury, was watching the Kiddie Korps. "I said, 'I better get over to him,' " Bourne said. "It was too late."

This season, the Islanders had trouble with overtime, winning only once in 14 games. Arbour dismissed any connection: "The season's over. That's in the past. Overtime means nothing at all."

The Islanders briefly held a 2-0 lead, relying on Capitals-killer Mike Bossy and captain Denis Potvin in the first half of the second period.

Bossy added the third goal to tie the score in the final two minutes of the second period when he redirected Potvin's slap shot from the point. With that, he tied Jean Beliveau for the second-most goals in NHL playoff history, 79.

But the Islanders never seemed to have command. For one very good reason: the Capitals outshot them, 42-17. "The shots on goal," Trottier said. "Why? Why, you ask. Look at the penalty sheet."

And there, you will find 15 Islanders penalties to 10 for the Capitals. Several Islanders bit their lips when asked about them. "The numbers are a little lopsided," said Bossy, "but, hey, I'm not calling the game."

"Take away those penalties . . . those things really got us into trouble," said Arbour. "We were two men short (when Larry Murphy scored the first of his two goals in 16 seconds), and we were reeling, but then we came back. We shouldn't be forced to kill penalties like that. It takes a lot out of our offense."

But that doesn't mean it has taken a lot out of the Islanders.

"As much as they might hope it's a psychological edge that they won this one," Trottier said, "it's not. You always hope this drives the nail in the coffin. I don't think it has."