Yannick Noah earned his first career victory over Bjorn Borg yesterday, 6-1, 6-2, in a quarterfinal upset at the $300,000 Monte Carlo Grand Prix tennis tournament in Monaco.

"I think for me it was the time to beat him," Noah, 21, said after dashing Borg's dream of a triumphant return to tennis following a five-month tournament break.

Noah, seeded sixth, meets top-seeded Ivan Lendl in a semifinal match Saturday. Lendl advanced with a rapid 6-0, 6-1 victory over No. 7 seed Balazs Taroczy.

Borg, who has dropped from first to sixth place in the rankings in the past 10 months, was seeded fourth in this clay-court tournament, which he has won three times. Borg, a native of Sweden now living in the tax-haven of Monte Carlo, had to go through the qualifying round because of his refusal to play in at least 10 Grand Prix tournaments this year.

Noah, a native of Cameroon, needed only 55 minutes to oust Borg. The Frenchman slammed in his fourth ace of the match in the final game to make it 40-15 and then ended the contest on his first match point with a forehand passing shot. It was the first time in five meetings Noah had defeated Borg.

Borg said he was disappointed, but not surprised by his loss. "I didn't expect to win the tournament after the long layoff I had," he said. "But I know how to take a loss . . . It takes time for a player to get back to his top level."

At Hilton Head Island, S.C., top-seeded Chris Evert Lloyd reached the quarterfinals of a $200,000 tennis tournament before rain interrupted play. The six-time titleholder in the tournament and defending champion, dominated Paula Smith, 6-1, 6-0, in a match that lasted less than an hour.