All season, the accusation has hung above the New York Islanders, just as their three Stanley Cup banners hang from the rafters at Nassau Coliseum.

The Islanders are flat. They're slumping. This is not the same team it was. They're bored. They're boring. They're spoiled by all that winning. What's wrong with the Islanders?

If their game Saturday night with Philadelphia is any indication, the answer might be "Nothing." A 4-0 first-period lead ballooned to a 9-2 decision in a game more reminiscent of what the Islanders can do come playoff time.

But the Islanders have not displayed that kind of hockey with any regularity, and some critics do not anticipate a Stanley Cup parade down Hempstead Turnpike.

Capitals Coach Bryan Murray wonders if the champions are simply not the superbly consistent team they once were. "They are playing well," he said, "but I still don't think you can hide a high level of play all year long and then turn it on in the playoffs. If they were as good as everybody wants to think they are, as good as they were, they would have shown it by now. But they've been able to hide behind the idea of 'wait till the playoffs' because to some extent the press has let them."

Last night's 3-1 loss to Boston left the Islanders tied with Washington for second place in the Patrick Division, trailing Philadelphia by 10 points.

"Maybe we were getting a little complacent earlier in the season," said Bob Nystrom, whose overtime goal in May, 1980, brought the Stanley Cup to Long Island for the first time. "Maybe we have had trouble getting up for some of the games. It's a long season, and maybe you just don't have the same energy for all the games."

This season, the Islanders have not forechecked consistently, and are not creating enough scoring opportunities, so goal production has dropped. A year ago, in 80 games, New York had 385 goals. After 75 this season, they have scored 280, falling below the league average for the first time since winning the Stanley Cup.

"It seems sometimes when we do get the chances, the shots go wide," said defenseman Ken Morrow. "We've had some frustrating times."

One of the most frustrating had to be a 6-0 loss to St. Louis two weeks ago. That was the sixth shutout of the Islanders this season; a year ago, they suffered one shutout. In 21 of New York's 25 losses, the Islanders scored twice or less, and have been held to a single goal 12 times.

The Islanders' power play, once so potent, doesn't see as much work as it once did. The opposition, no longer afraid of the Islanders as all-dominating, is not drawn into as many penalty situations.

The best illustration: against the Flyers last season, the man-advantage unit had scored 14 goals in 41 chances; this season, in 23 tries, it has produced four goals.

Until Saturday, the Islanders had not beaten Philadelphia all season, and their last two meetings had produced shutouts by rookie goaltender Bob Froese. They have not beaten Minnesota or Boston, and the Islanders have the dubious distinction of being the only NHL club to lose all three of its games with lowly Detroit.

Only twice this season have the Islanders, when trailing as they entered the third period, come from behind to win. Once, in the fourth game of season and again two weeks ago in a 4-3 game in Pittsburgh.

One sore point that all the Islanders' players skirt in conversation has been the performance of Bryan Trottier. An intense, workaholic-type player who never used to quit, Trottier has accumulated more than 100 points in each of the last five seasons. He has 82 now (31 goals, 51 assists), and isn't likely to surpass the 100 mark because his play lacks its former punch.

Trottier will not talk about the presence of any problem, saying only, "I can only play as well as the guys around me."

Because the "guys around" Trottier look to him for leadership and haven't found much this season, the situation has become a circle of frustration.

Linemate Mike Bossy, who has teamed with Trottier so successfully in each of his 50-plus goal seasons, refuses to criticize his teammate's performance. "Ask Bryan," he says when asked what is wrong. Privately, however, he has indicated he is puzzled and less than ecstatic with Trottier's play.

After the Islanders beat New Jersey, 9-5, last week, a game in which Trottier scored one goal and had three assists, Nystrom said, "Now he's getting into it. A little more aggressive. I enjoy seeing him like that again."

Glenn Resch, the former Islanders goaltender now playing for New Jersey, was more candid. "Bryan needs to catch fire," he said. "They go the way he does, and if he can get catch fire the way he used to, they'll be fine. They've certainly got the goaltending."

Goaltending--Billy Smith, who will do anything to win, and Rollie Melanson--and the Islanders' penalty-killing units have been the saving grace in New York's up-and-down season.

In 16 of their last 23 games, the Islanders' penalty killers have shut down the opposition's power play, and have successfully killed 59 straight penalties on home ice since early January. The Islanders' short-handed unit ranks second in the league.

There have been times this season when the Islanders did skate and dominate as they used to, as in their last two meetings with Washington.

Heading into the playoffs, what will the Islanders do to prevent a rude sendoff into an early summer?

"I think (against Philadelphia) we played more the kind of game we know we've got to play from now on," said Coach Al Arbour. "Hopefully, we've put our pop guns away and taken out our shotguns."