NEW YORK, DEC. 2 -- Eighth-seeded Brad Gilbert upset No. 4 Jimmy Connors, 6-4, 7-6 (7-5), in the opening round of the $500,000 Masters tennis championship tonight.

Connors, who hasn't played a tournament in 7 1/2 weeks, has been suffering from an ear infection. "I don't feel too good and I don't like to play under these circumstances," said Connors, who had beaten Gilbert in five of their last six matches.

Gilbert and Connors are the only Americans in the Masters, a round-robin tournament featuring the top eight players in the world. Each competitor plays three matches to determine who advances to Sunday's semifinals.

In other opening-night matches, second-seeded Stefan Edberg of Sweden defeated No. 7 Pat Cash of Australia, 6-4, 4-6, 6-1, and third-seeded Mats Wilander of Sweden beat No. 6 Miloslav Mecir of Czechoslovakia, 6-4, 6-1.

The match was a replay of the Australian Open final in January, which Edberg won in five sets. Cash, the 1987 Wimbledon champion, beat Edberg in their only other meeting of the year, at the Queen's tournament in England.

Edberg took command in the final set when Cash double-faulted to lose the fourth game.

Edberg broke Cash again in the sixth game to take a 5-1 lead and held serve to win the match, closing it out with a backhand pass down the line.