A year ago, when the New York Islanders won their second straight Stanley Cup, they needed only 18 games to pour the champagne. Tonight, in Boston Garden, the Quebec Nordiques will be playing their 12th game, with as many as 14 more remaining if they are successful.

Down, 3-0 and 5-2, to the Bruins Friday night in Quebec, the Nordiques rallied to create a 5-5 tie before they were undone by Peter McNab's goal at 10:54 of overtime. It was the fifth playoff goal for McNab and, appropriately in this whacky postseason, he has already noted that he is certain to be traded because a lot of folks in Boston are unhappy with his style of play.

While Quebec has gone the limit in its first two series, eliminating Montreal in a fifth game at the Forum before playing Boston, the Islanders have worked harder than expected, too. Forced to overtime of the fifth and final game to oust Pittsburgh in the first round, the Islanders had their hands full before finally knocking out the injury-plagued Rangers in six games.

The end came Friday night in Madison Square Garden, where Dave Langevin's second goal in 50 Stanley Cup games broke a 3-3 tie and lifted the Islanders to a 5-3 victory. It was a grateful Islander team that, after 11 games in 17 nights, looked forward to a weekend of caring for wounds and aching muscles.

"It was the most important goal I ever got, going back to high school tournament time (in Minnesota)," Langevin said, "because the Rangers were coming on, they were playing well and we didn't want to go to seven games."

"The Rangers had every reason to quit," said Butch Goring, a two-goal scorer. "They had all kinds of injuries and they had all kinds of excuses, but they didn't give up. That was the best game of the series. There was a lot of intensity and emotion."

When it was over, the 17,390 Madison Square Garden fans gave the Rangers a lengthy ovation, a well-deserved tribute to a team that had overcome adversity from the opening of the season, when injuries took away star forwards Anders Hedberg and Ulf Nilsson.

On the first shift Wednesday at Nassau Coliseum, the Rangers lost center Mike Rogers to a knee injury that required surgery the next day. Rogers not only was the club's high scorer, he was the only player who suited up for all 80 games of the regular season.

Nevertheless, the Rangers won that game, 4-2, and Friday night they rallied three times to tie the powerful Islanders. They appeared to do it a fourth time, too, and there was disbelief when Islander goalie Bill Smith somehow blocked a close-range shot by Reijo Ruotsalainen with 2:56 left. This time, the Rangers could not manage the tie, and for the 42nd straight season there will be no Stanley Cup parade down Broadway. Don't rule it out in the near future, however. As Coach Herb Brooks pointed out afterward, this is a team that is moving forward.

"All I said to them (the players) after the game was, 'Thank you,' " Brooks said. "It was another one-goal hockey game and we played one-goal games in five of six, if you discount empty-net goals in two of them.

"I think this series showed we belong in the top echelon of hockey clubs in this league. We were in the top half-dozen or so and next year we should move up, although each step from here on is tougher than the last.

"We had lots of adversity this season and some people's adversity is others' opportunity. Some of them made the most of it. I think we have some depth, no question about it, and it'll be a very spirited training camp next year for spots."

Brooks touched on another reason why the Rangers will be much better next year, but modesty prevented a full evaluation. This was Brooks' first year in the NHL and he had to erase some doubts about his own ability before he got some players to follow his instructions.

"It's been an interesting year, a year of analysis and study," Brooks said. "I think next season I'll be a better coach. It's taken me time to understand some things and adapt myself to certain things."

The Rangers, it will be recalled, lost their first three games in horrible fashion and were 3-8 after four weeks. They finished 39-27-14, with the seventh-best record in the NHL.

"I felt from the start that the winner of this series would win the Cup," Brooks said.

There is no reason to change his opinion now that his team can't win. The rest should enable the Islanders to get off to a fast start against either Boston or Quebec when the Prince of Wales Conference series begins at Nassau Coliseum Tuesday. And the final seems destined to be an anticlimax, since both Chicago and Vancouver, who open the Campbell Conference finals Tuesday at Chicago Stadium, had sub-.500 records.

The Black Hawks, fourth in the Norris Division, continued their upset pattern Friday by eliminating the St. Louis Blues, 2-0, in the sixth game of the Norris Division final.