Somewhere on Long Island, they're yelling, "Break up the Capitals!"

Last night Washington defeated the Stanley Cup champion New York Islanders, 3-1, for only the fourth time in history, and the Capitals moved into a third-place tie with the idle New York Rangers in the NHL's six-team Patrick Division.

The New Yorkers began flat before the Capital Centre crowd of 14,131 and stayed that way, except for a short burst of muscle in the third period. But by then, Washington had the game in hand, thanks in large part to the goaltending of Al Jensen.

Jensen is 3-0 since being recalled from Hershey, yielding only three goals in his three starts. And tonight he extended his shutout streak to 124 minutes 8 seconds before a third-period goal by Clark Gillies. It broke the Capitals team mark of 119:01 established by Dave Parro, who has replaced Jensen at Hershey.

The Capitals took command early, with Mike Gartner's power play goal in the first period. Gaetan Duchesne and Bobby Carpenter added one each in the following periods. Gillies, who had tried all night to connect, finally got a shot past Jensen at 10:37 of the last period, but if it was to be an Islander rally, the spark didn't take hold.

"We're not clicking together," Coach Al Arbour said of his Islanders, shut out, 2-0, on Thursday by Minnesota. "We've missed the net so much lately--tonight Clarkie (Gillies) missed two open-net chances, Brent (Sutter) missed one. We're missing obvious things."

One obvious missing thing was Islanders defense: Denis Potvin, out with a neck injury, and Tomas Jonsson and Mike McEwen were not in the lineup last night. "That's a big part of it," Arbour said, adding, "No, it's not a panic situation."

Capitals Coach Bryan Murray, openly delighted, agreed that the Islanders "were missing a couple guys. And I don't feel sorry for them at all," he added with a grin.

The Islanders felt sorry enough for themselves after a frustrating night in which they missed too many easy shots.

Bryan Trottier responded to questions with a curt, "We don't have any answers."

During the first period, the Capitals repeatedly pressed the New York club into giving the puck away, although they could not complete any plays until the Gartner goal. Roland Melanson, in goal for New York, saw 12 shots that period.

Washington's first power play dissolved into nothing, but at 16:29, with Gillies out for a trip, Gartner took the puck around the Islanders net, passing to Rod Langway on the point. Langway's shot missed, but the rebound was shoved in by Gartner on an assist by Carpenter to give the Capitals a 1-0 edge.

They sat on that edge throughout the second period, effectively killing Scott Stevens' interference penalty at 11:43. Then Duchesne built up the advantage.

"The shift had changed, I came on," he said. "I saw Ken Houston skating around the net with the puck." Houston couldn't get an angle on the shot and the puck skittered out to Glen Currie. "I called to him, 'Glen, give it to me,' " Duchesne said. "But he didn't hear, or anyway, he took a shot."

Currie's attempt flew short, but Duchesne was all eagerness to get a piece of it, and did. "It came to me, I lifted it, and he (Melanson) did this," he said, motioning a somersault.

That lifted the Capitals' spirits higher, and suddenly the three-time champions looked more like the Washington club seen in these parts throughout the past. Bob Nystrom had predicted his team would "come out flying" against Washington, but instead the New Yorkers were totally grounded.

"I think we played to their strengths," Murray said. "I put Doug Jarvis where he'd be on Trottier, and he was great. It paid off. Sometimes that doesn't work out. But this time our strength against theirs worked well."

Gillies' goal in the final period might have helped the Islanders muscle back into the game, but Washington shut down any New York offensive drive with a goal of its own.

Milan Novy, skating in on Melanson, carried the puck to just outside the cage, then flipped it to Carpenter for the goal that made it 3-1 at 13:38.