Someone else will have to do for the U.S. Open what Billie Jean King did for Wimbledon two months ago -- enliven it with the defiance of natural law and the possibility of outrageous sentiment.

Today, King, who is 38, looked her age. On the first day of the U.S. Open, she lost a first-round match, 6-3, 6-2, to Sue Mascarin, 20 years her junior.

"Everyone said, 'Just forget it's Billie Jean, don't look at her,' " said Mascarin, who is ranked 51st in the world and never before had beaten anyone so important. "She's very intimidating on court. She is a legend."

Mascarin's coach, Owen Davidson, who won doubles titles with King in 1967 at Wimbledon and the U.S. championships, told her not to look King in the eye. "She tries to get your eye," Mascarin said. "She'll look at you. I think she could easily outstare me."

But King, seeded 13th, couldn't outplay her. By her own count, King made only two forehand volleys all match, only one 30-30 point. She looked ragged, she looked rusty, she looked old. "One of those days," she said.

It was not the nicest way, the sentimental way, for the Open to begin at the National Tennis Center. Everything else, however, went according to form. Ivan Lendl, the third seed, beat Ramesh Krishnan, 6-4, 7-6 (8-6), 6-1. Krishnan double-faulted at 6-6 in the tie breaker to give Lendl the only edge he needed. Lendl aced him to finish the set. Lendl, who was under considerable scrutiny because he was the top-seeded man in action and because he never has won a Grand Slam event, said, "I'm 22 years old, I feel I'm good enough to win one of the big ones. If I don't, I'm not going to quit. I have a few more years."

Asked what he had to do to overcome the psychological great divide of winning a major, Lendl said tartly, "There is no psychological barrier. You're trying to build one for me. You'll not hear it from me."

Guillermo Vilas, the fourth seed, struggled briefly and early, but beat Chris Dunk, a qualifier, 6-7 (7-3), 6-3, 6-4, 6-2. Mats Wilander, the 17-year-old Swede who sheared his golden locks (by his own hand) this summer so he would not be recognized, was in recognizable form, beating Bill Scanlon, 6-4, 6-3, 6-1.

Chris Evert Lloyd, the No. 2 seed, easily, perhaps too easily, defeated Pilar Vasquez, 6-1, 6-0. Evert would dearly like to win her sixth Open and salvage an otherwise disappointing year (she lost to Martina Navratilova in the Wimbledon final and to Andrea Jaeger in the semis of the French Open), almost as much as she would like to derail Navratilova's express.

"After Wimbledon, she (Navratilova) said she would like to be known as the best woman player of all time," Evert said. "That may be very possible in five or 10 years. I'm a little insulted. Billie Jean and Margaret Court, they have 10 times better records. I have a better career record."

When asked if she had sympathy for Navratilova, who has been suffering from an apparent case of food poisoning, Evert replied, "As a friend, I'm concerned. As a competitor, a rival, Martina has said all year every single interview she's the best player; that no one could beat her if she's playing half decently. She's very confident. It's hard to feel sorry for her when she's a little overconfident. I feel she puts pressure on herself by boasting the way she does."

Dr. Irving Glick, the tournament physician, said both Navratilova and Tracy Austin, who underwent untrasound treatments today for tendinitis in her right shoulder, were feeling better.

Though King succumbed, age was well served by Stan Smith, the 1968 NCAA champion, who beat Mike Leach, the 1982 NCAA champion, 4-6, 6-4, 6-3, 7-5. Smith, who won the Open in 1971, is 35 now and grateful, elated, by days like this, especially since he has been "struggling all year, getting sick."

King, who had to pull out of the Canadian Open two weeks ago because of a bad knee, said she was feeling 100 percent now. She has been at home with her knee elevated. "Physically, I feel terrific," she said.

The lapses seem to be of another kind. King won the first three games of the match and then lost the next seven. "Nothing went right," King said. "She's (Mascarin) had two good weeks. She did well at the clay courts (losing in the quarterfinals to Kathy Rinaldi) and Atlanta (losing in the final to Evert). She's much more match-tough than I am at the moment."

With King serving at 2-1 in the second set, Mascarin broke her, or really King broke herself with four unforced errors. It was 3-1, youth. The crowd of 15,461, many of whom were jammed into the stadium to see the old lady who has won this tournament three times, began to chant, "Come on, Billie, come on."

Momentarily, she did, breaking back to make it 3-2. Four unforced errors later, King lost her serve and her best chance to stay in the match. Mascarin held to make it 5-2 and King served again to no avail. At match point King missed her first serve and had to stay back. Mascarin pinned her in the corner with a deep shot and volleyed the return cross court the other way.

King trotted to the net in the dress that carried her to the Wimbledon semifinals, trying not to look weary. "I was trying as hard as I could," she said. "Nothing was going right."

King remembered the last time she lost in the opening round of the national championship. "I had a match point and lost," she said. "Justina Bricka hit a spinning serve that hit the chalk," she said.

And she remembered a time when she was just a bit younger than Mascarin is now and she had to play her elder. "When I was 15 I played Margaret DuPont in Philadelphia. She was quite a bit older," she said. "She won, 8-6, in the third. She was very nice to me. She said, 'This may be the last time I'll ever beat you.' I never played her again."