It was playoff preview time today and the New York Islanders won the battle from the Washington Capitals, 6-4. In the long run, it could have cost them the war.

Center Brent Sutter, a 100-point man, injured his right shoulder late in the second period when he was checked by Washington's Larry Murphy. Sutter was taken to Nassau County Hospital and, although the Islanders said no details on his condition would be available until Monday, it appeared that the shoulder had been dislocated.

"It was very frustrating," said teammate/brother Duane Sutter. "I wanted to jump out there and grab the guy who hurt him and start hitting him, but you're not going to prove anything doing that and it was a clean check. If it had been some kind of a cheap shot, we'd have had a right to be upset."

The entire 60 minutes proved frustrating to the Capitals, from the moment Mike Bossy put the first shot of the game behind Pat Riggin until Duane Sutter wrapped it up with a fluke shot from the right-wing boards that skipped into the net off Riggin's right pad.

"We had plenty of chances to win," Washington captain Rod Langway said. "We got four goals and that should have been enough. But we can't give away so much defensively."

Although Riggin looked bad on the clincher, he made a number of good stops, with his 24-save total including two third-period breakaways by Bossy. At the other end, Kelly Hrudey's 29 stops frequently inspired chants of "Roo-dy" from the sellout crowd of 16,002.

"We're playing a lot looser in our defensive end and it's hurting us," Capitals Coach Bryan Murray said. "We're giving up too many chances and too many goals. We gave up more chances in this game than we did the last three or four against them."

The Capitals had beaten the Islanders three straight times, but the situations of the clubs have altered dramatically in recent weeks. The Islanders, whose 28 losses match their high over any of the last 10 seasons, are unbeaten in their last five games. Washington has lost four of five.

As a result, the Capitals have fallen four points behind first-place Philadelphia in the Patrick Division. The Flyers beat the Maple Leafs, 6-1, tonight in Toronto and, as the Flyers have a game in hand, it increasingly appears that the Islanders will be Washington's first-round opponent.

There was reason to believe the Capitals could get back on the winning track tonight, when they rebounded from Bossy's stunning first-minute goal to take a 2-1 lead on scores by Larry Murphy and Craig Laughlin.

Although Washington outshot the home club by 16-12 in the second period, New York scored four times to take a 5-4 lead. Two Islanders goals came with each team a man short, a circumstance that has benefited New York in the past.

Denis Potvin's 40-footer tied it at 1:20, then John Tonelli beat Riggin with the first of his two goals, a close-up backhander. Bob Carpenter's 48th rebuilt the tie, as he knocked the puck in the air and Islanders defenseman Paul Boutilier, trying to bat it away, dropped it into his net.

Ken Morrow's first goal, in his seventh contest since returning from knee surgery, was matched by Mike Gartner's 43rd on a power play. But the killer for Washington was Tonelli's second goal of the game, only nine seconds before the buzzer.

Each team was a man short when he put the puck over Riggin's right shoulder from the right-wing circle. The goal came a few seconds after Brent Sutter was helped off and it served to lift the spirits of the Islanders, who desperately needed a boost at that point.

"In my mind, Brent has been the MVP in the league," said Morrow. "He's played great every game this year and, if he's not around for the playoffs, it's going to hurt us bad."

Duane Sutter, who turned 25 today, celebrated with the big third-period goal that iced things, as well as two fights that sent Peter Andersson and Carpenter to the penalty box with him.

Andersson, who received his first major penalty in the NHL, said, "I just took him into the boards and he dropped his glove. You need to drop your glove when that happens. As we get closer to the playoffs, there's more need to prove yourself that way. Maybe now I'll practice on the bag, so I can hit back next time."

The eventual penalty total listed the Capitals for 36 minutes, the Islanders for 34. Scott Stevens had six and another case of the frustration that has plagued him in his meetings with the Islanders.

In the first period, Pat LaFontaine banged Stevens against the boards and Stevens fell on him, to be penalized for "cross checking."

In the second period, Stevens checked Bossy at the blueline. Shortly thereafter, Bossy used his stick on Stevens, who rammed Bossy against the boards and held him there. Play was at the other end when their altercation was noticed and Islanders Gord Lane and Bryan Trottier raced to Bossy's aid, escalating what was essentially a static situation. The only penalties were a double minor to Stevens, a single to Bossy.

"It's kind of frustrating, the stuff they get away with," Stevens said. "It gets me so mad. When Duane punches Bobby, they get the same. When Tonelli punches Larry, there's no extra two minutes. But when I'm involved in something I don't even start, I get the extra two. So many bad calls, I can't handle that."

Dave Shand had reason to be unhappy, too. He was whacked on the head by Bossy's stick in the third period, with only a headache the result.

"He caught me in the temple and I was woozy," Shand said. "No stitches and no penalty. Another great Bob Myers call."