Steffi Graf moves on from historic Slam to quest for Olympic gold. West German teen-ager appears capable of dominating women's tennis for next decade

What do you do for an encore after you've won the Grand Slam of tennis? If you're Stefanie Maria Graf, you take immediate aim at an Olympic gold medal. No player has ever won both, let alone in the same season. Graf won the singles four years ago when tennis was revived in the Olympics as a demonstration sport. This time it's official.

``The scheduling is not the best, but I'm excited to go,'' said Steffi the Unstoppable before boarding a plane for her native West Germany, where she plans to relax for all of two days before setting off for South Korea.

``It will be fun being with other young athletes from around the world,'' she said looking forward to the tennis competition in Seoul, which begins a week from Wednesday and concludes with the women's final on Saturday, Oct. 1.

Steffi had changed from her tennis whites into her favorite attire of faded jeans and a t-shirt, had let her ponytail down, and looked every inch the teen-ager she is. At 19 and still improving, she could dominate her sport for the next decade if her enthusiasm holds.

``Don Budge told me he knew all along I would win the Grand Slam - and can do it a couple more times,'' she said after beating fifth-seeded Gabriela Sabatini 6-3, 3-6, 6-1 in the US Open finals Saturday afternoon at Flushing Meadow.

Budge won the first Grand Slam 50 years ago at nearby Forest Hills. Like Graf, he beat his doubles partner, Gene Mako, in the final.

Said Graf, ``There are no surprises when Gaby and I play. I used a drop shot on big points more than usual, and that worked. She got tired in the third set, and I played better than in the second set.''

Facing Graf at her best is like playing against a supercharged ball machine. It is a testimonial to her talent and determination that she won Saturday while playing less than her finest tennis.

After Sabatini won a tense second set, Graz lifted her game a level and shot out to a 3-0 lead in the last set, breaking Sabatini at love in the second game. Champions have a way of doing that.

``Until then, I was afraid to hit through the ball,'' Graf said. ``It was very windy, and I was trying to keep the ball in play instead of going for winners. Toward the end, I was more aggressive.''

The world already knew that Graf had the fiercest forehand and fanciest footwoork in women's tennis. What became much more apparent during the Open is that her stamina also sets her apart. She was energetically hopping, skipping, and jumping from place to place throughout the fortnight.

``I know when a match is staying close that my fitness will help me later,'' she said. ``That's an important factor in my success. In the second half of the match, I moved Gaby from side to side and wore her down,''

The 18-year-old Sabatini, the first woman from Argentina to reach a Grand Slam final, is the only player to beat Graf this year. She did it twice last winter, pouring her heavy topspin ground strokes deep into Graf's backhand corner.

Her game plan was the same here. But as she and Graf agree, Steffi gets a stronger glint in her eye for major championships.

Graf is only the fifth player to win a Slam, and the first since Margaret Smith Court in 1970. Says Court, ``I like the brisk, straightforward way she plays. She's out there solely to win, and she gets right on with it. I don't see anyone around today who can stay with her.''

Graf, a trim 5 ft. 8 in. and 125 pounds, beat four different opponents around the wold to win the Slam. In Australia, she defeated Chris Evert, 6-1, 7-6. At the French Open she shut out Natalia Zvereva of the Soviet Union, 6-0, 6-0. And at Wimbledon she downed Martina Navratilova, 5-7, 6-2, 6-1.

The change at the top in women's tennis has been sudden but complete. A year ago, Navratilova won three titles here, the singles and both women's and mixed doubles. This year, she left with none.

This was the first US Open since 1974 in which neither Navratilova nor Evert reached the final. Evert defaulted her semifinal match against Graf because of illness. Sabatini beat Zina Garrison in the other semi, after Garrison had knocked out defending champion Navratilova in the quarterfinals.

It was Graf's first US Open victory in five tries, and because of a new format this year she was the first woman to have to go seven rounds to win it. The triumph was worth $275,000 plus a special bracelet with four diamonds, one for each Grand Slam victory.

She is not the youngest woman to win the Slam. The late Maureen Connolly did it at age 18 in 1953. (The other Slam winner in addition to Budge, Court, Connolly, and Graf, and the only one to accomplish the feat twice, was Rod Laver, in 1962 and '69).

Graf, the picture of poise on the court, was barely emotional over her historic accomplishment. Her discipline can be difficult to believe.

``I need time to think about it,'' she said with a modest smile. ``It's a nice relief. I'm happy to gt it over. There's no more pressure. People kept telling me I couldn't lose here, and that bothered me. It was more of a mental strain than a physical one.

``It was never my goal as a young girl to win the Slam. I haven't read a lot of tennis history. But I know it's very important. It's a special thing - the best you can accomplish.''

Eventually it will mean more to her. In the meantime, she goes on to the Olympics in quest of more if not greater glory.