Andrea Jaeger stunned Chris Evert Lloyd in yesterday's semifinals of the Family Circle Cup women's tennis tournament at Hilton Head Island, S.C., with a 6-1, 1-6, 6-2 victory built on base line lobs and a steady ground game. It was only the third loss on clay by Evert in 202 matches dating back to August 1973.

Jaeger moved into today's final against Martina Navratilova, who beat Mima Jausovec, 6-1, 3-6, 6-2.

Jaeger, seeded third, is the fifth woman player ever to defeat Evert on clay and the first to beat her at the Family Circle, in which Evert had not lost in 32 matches and 65 sets. She won the event the last six times she competed.

Both players ascribed the victory to Jaeger's lazy bloopers from the base line, which Evert admitted she couldn't smash and didn't have the patience to return in kind.

"I guess I just wasn't willing to stay out there all day and moonball back," she said. "It's frustrating. All the players feel that way. We don't think it's attractive for women's tennis . . . I know how to beat her, but I don't have the right frame of mind."

Jaeger said her base line-hugging strategy, which yielded many long rallies, including one with an incredible 125 shots in the final game, worked better than anything else she tried.

Evert said the loss may give her the incentive she needs in a season that hasn't provided her with a major goal yet. "I need goals and I don't have any," she admitted. "I need to be really hungry for a title."

In the third set, Jaeger seemed to be able to reach anything Evert hit to her, even managing during one rally to recover a dropped racket, although she lost the point.

In Monaco, top-seeded Ivan Lendl and Guillermo Vilas, the No. 2 seed, reached today's final in the $300,000 Monte Carlo Grand Prix tournament after both survived close semifinal matches.

Vilas needed 2 hours 50 minutes to eliminate his Argentine countryman Jose-Luis Clerc, 7-6, 7-5. Vilas saved seven set points in the first set and rallied to win the second-set tie breaker, 8-6. Lendl, ranked second in the world, served six aces in a 6-1, 1-6, 6-1 semifinal victory over Yannick Noah. It was the first time Lendl had lost a set in this clay court tournament.

The title match carries a winner's purse of$60,000. The runner-up will get $30,000. Clerc and Noah each earned $14,600 as losing semifinalists.