Three of tennis' "Four Musketeers" will be watching today as John McEnroe of the United States plays Yannick Noah of host France in the opening singles match of the Davis Cup championship in Grenoble.

American Gene Mayer will play Henri LeConte in the second match as a result of yesterday's draw. In Saturday's doubles match, it will be McEnroe and Peter Fleming against Noah and LeConte. Play concludes Sunday with McEnroe playing LeConte.

McEnroe and Noah have played each other once before--in the Sunshine Cup in 1977, when McEnroe won. The United States is the defending champion.

"It's a great draw for us," said Arthur Ashe, nonplaying captain of the U.S. team. "I always wanted John to play first and last, and that's exactly what's happening."

Three of the Four Musketeers who won the Davis Cup for France from 1927 to 1932 are attending the matches. Jean Borotra is 84, Henri Cochet 80 and Rene Lacoste 78. The fourth, Toto Brugnon, died in 1978.

It's the biggest tennis occasion for the French since Britain won the Davis Cup from them in 1933. The previous year, the Four Musketeers had won the trophy for the sixth time by defeating the United States . . .

In Sydney, unseeded Leslie Allen upset No. 5 seed Hana Mandlikova, 3-6, 6-2, 6-1, to advance to the quarterfinals of the $125,000 New South Wales Women's Open . . .

The promoters of the $150,000 Virginia Slims of Washington tournament, wanting to avoid a conflict with a Redskins game that will be played in RFK Stadium Jan. 9, have rescheduled the tournament finals at Capital Centre for Jan. 10, at 7:30 p.m. The finals had been scheduled for Jan. 9, an open date for the Redskins before the football strike necessitated a schedule change.