The Washington Capitals and New York Islanders will stage a preview of the upcoming Stanley Cup playoffs tonight at Capital Centre. The Capitals are counting on favorable reviews to bring the two clubs back to the Centre for the April 6 commencement of Washington's first playoff series.

In what has been characterized as a superseason here and a year of disaster on Long Island, the teams enter the game tied for second place in the Patrick Division with 92 points. Each has two games to play after tonight's confrontation and, should the clubs finish tied in points, the Islanders would earn the second spot, an extra $1,000 per man and home-ice playoff advantage on the basis of more victories.

"We definitely want second place, with home ice to start the playoffs and the extra game if it comes down to that," said Washington center Doug Jarvis, whose four Stanley Cup rings top everybody else in tonight's contest. "It's also important to prove to ourselves that we can beat them, probably more so than proving it to them."

The Capitals have been thrashed, 8-3 and 6-2, on their last two visits to Long Island, after enjoying considerable early season success against the Islanders. New York comes here with a 3-2-1 edge in the season series.

"Although it would not be devastating if we lost, it is very important to finish second," said Washington Coach Bryan Murray. "The biggest factor is to make the most of what we've achieved. Second in this division would be a heck of an achievement where we've come from.

"It's also important from a confidence point of view and in coaching against Al Arbour, which is no easy chore at any time. His having the last change and dictating the matchups could be a key factor in their building. The benches are so far away, it's difficult to make good line changes on the fly."

Washington has won only one game in 22 visits to Nassau Coliseum, a 5-1 decision in December that marked the Capitals' 14th straight game without defeat. At the Centre, the Capitals have been more successful, posting a 4-12-4 record that includes a victory and a tie earlier this season.

The Islanders, who have won three straight Stanley Cups, possess vastly more playoff experience than the Capitals, 1,339 individual games to 253. Sixteen members of the current New York team have played on all three championship clubs.

"This is a big game for our younger players," Murray said. "It provides playoff experience with a free chance. You might call it a dress rehearsal for the real thing. There are a few things I'll be trying, experimenting with, and hopefully some will work."

The Islanders, who struggled through much of the season, apparently have straightened themselves out, winning four of their last five. But New York suffered a blow Sunday when winger Clark Gillies suffered a strained ligament in his left knee when he was checked by Pittsburgh's Tony Feltrin.

Gillies will be fitted with a brace and is expected to resume skating Friday, but it is questionable whether he will be ready for the playoff opener. Defenseman Gord Lane, the onetime Capital who needed thumb surgery in February, has been scouting Washington from the press box for the last few weeks.

The Capitals are in good health for this one, with Bengt Gustafsson ready to resume his place on the No. 1 line with Dennis Maruk and Mike Gartner after missing two games last week with a strained back and bruised thigh.

"Life goes on. I'll be all right. But I'm getting too old for all these bumps and bruises," said the oft-injured Gustafsson, who clebrated his 25th birthday a week ago.

"Gus makes things happen," Murray said. "He's so good with the puck and he's starting to shoot the puck more now, which has got to help him and the team."

Pat Riggin will tend the Capitals' goal tonight, his first start against the Islanders since October, and Murray indicated that if Washington should win, Riggin also would be the starter in the first playoff game.

Although this shapes up as the Capitals' most important game of the season, about 4,000 tickets were still unsold yesterday. Attempts to characterize the contest as the biggest in the team's history have flopped, because even a casual Capital fan can recall two of greater import.

On April 3, 1980, the Capitals blew a 2-0 lead in Philadelphia and lost, 4-2, when victory would have assured a playoff berth. On April 4, 1981, a 4-1 loss on Long Island permitted Toronto to edge Washington out of a playoff spot the next day.

The 4-4 tie with Pittsburgh Saturday and the 5-4 loss to the New York Rangers Sunday inspired fears that the Capitals were ready for another April flop, but captain Rod Langway, the key to this season's turnabout, said the club would be ready tonight.

"We had a tough schedule last week, with that Vancouver makeup screwing up the schedule and giving us four games in five nights for the first time," Langway said. "Maybe we've been excited about the playoffs, but we have three games to play and we know we can't turn it on and off.

"We're back to being healthy, we've got a good remaining schedule and we've got to get home ice in the playoffs. We have to win Wednesday and then get three points from Detroit and the Rangers. Everybody knows what he has to do.