The Montreal Canadiens have won their third straight Stanley Cup, but each year it gets tougher. In 1976, the Canadiens lost only once in 13 playoff games. At that rate, they might even lose the Cup by 1984.

"Now I know how Alydar feels," said horse owner Gerry Cheevers, whose Boston Bruins were runners-up a second straight year. Alydar has beaten Affirmed a couple of times in the last two years, ujust as the Bruins have won a couple from montreal - two of the team's last 16 meetings.

The Canadiens, who have lost only 29 of 240 regular season games over three years, do not figure to get any weaker . For starters, Montreal next year likely will have the services of Mark Napier, the 21-year-old right wing who has scored 136 goals in three World Hockey Association seasons.

While the Canadiens drink from the Stanley Cup wihtout fear of outsiders' germs, the World Ice Hockey championships continue to be a Soviet-Czech monopoly. Canada's representatives this year, culled from playoff nonqualifiers and preliminary- round losers, earned the bronze medal with a 500 record.

Next year the World Championships will be contested in MOskow, April 14-27. The NHL regular season ends April 8, so there will be no opportunity to add early playoff dropouts. Canada, unless there is some application of common sense, will be represented by a team collected from the six nonqualifiers and permitted less than a week to practise together.

While this group is being slaughtered by the finely honed Czechs and Soviets, the Canadiens will be waltzing past the No. 8 team in the NHL in four, or if they match this year's indifference, five games. They then will sit around before doing the same to the No. 4 C club, and, despite the protestations of Boston Coach Don Cherry, the No. 2 team as well.

There are obstacles, financial and otherwise, but it would seem that administrators of a slowly dying sport would see the wisdom of sending the Montreal Canadiens to Moskow, where they can prove or disprove that they are the gratest hockey team ever assembled.

The early rounds of the Stanley Cup could be contested among the second through 13th teams in the NHL - or, assuming a further expression of sanity, the second through ninth. Then the Canadiens could return to face the survivor for the Cup.

It probably would make for a better final, since the Canadiens could be expected to suffer a letdown, fighting for possession of an old silver trophy instead of world supremacy. They would have trouble adjusting to NHL style hockey after skating on the big European rinks, too.

This proposed format would not designate Montreal as the team assigned to the World Championships. Give the top club in the regular season that honor, just in case someone else should finish first some time. That might even add a touch of incentive to the eternal boredom of a 720 game regular season in which nothing more is at stake than playoff seedings.

Sam Pollock, the Canadiens' capable general manager, does not like this idea. That is understandable. The Canadiens make a lots of money pedling Stanley Cup tickets at $17.50 each and, besides, it is a difficult assigment trying to find any NHL executive willing to change anything except his pants.

"it's unrealistic," Pollock said. I don't see it happening. We're a member of the national Hockey League and our obligation is to the NHL. It's important for us to be here in the Stanley Cup, not overseas playing exhibition games.

"There are a certain number of people who think Canada has to win every game overseas. I don't see it that way."

There are a certain nember of poeple, Pollock included, who think the Canadiens should win every game they play. A lot of other people are getting bored watching it, however, no matter how skillful the Canadiens' methods.