Andrea Jaeger, the 15-year-old tennis prodigy, was practicing against Martina Navratilova yesterday morning and went to retrieve some balls that had strayed from their court at Georgetown University's Yates Field House. Instead of going around the net on an adjacent court, she casually vaulted over it, as effortlessly as O. J. Simpson hurdling an airport rent-a-car counter. She gathered the loose balls with a few deft flicks of her foot. Johan Cruyff would have been impressed.

"The kid's an athlete," remarked an admiring bystander.

You can bet your $150 Fila warm-up suit she is.

Washingtonians this week have had their first look at the latest wonder women of tennis, Jaeger and 18-year-old Hana Mandlikova, in the $250,000 Colgate Series Championships at Capital Centre.

It has not been an entirely satisfying introduction. For the second year in a row, the early days of the eight-woman, all-star tournament have not lived up to great expectations. This is partially attributable to the fact that the players are coming off a three-week Christmas break, with no lead-in tournament under similar playing conditions. Starting next year, the tournament likely will be played before Christmas, which should help.

Maybe next time there will be no defaults either. Last year Evonne Goolagong Cawley hurt her wrist, this year Chris Evert Lloyd got the flu. Unfortunately, in tennis there are no substitutes waiting on the bench.

Perhaps the tournament will come alight in tonight's semifinals, or Monday's final. Meanwhile, we have seen enough of Jaeger and Mandlikova, the vanguard of the new generation, to form some impressions.

The kids are athletes.

Jaeger loves playing soccer almost as much as tennis. Toss her a basketball and she'll strike up a game. Mandlikova, daughter of a two-time Olympic sprinter, showed grand promise in track and field, played ice hockey on her older brother's team and loved to ski. They play an exciting, athletic brand of tennis that may be a hallmark of the future.

Evert dominated women's tennis for four years from the baseline, inspiring comparisons with Maureen Connolly of the 1950s and Helen Wills of the '20s. Suddenly, legions of two-fisted teens were imitating the style.

Navratilova -- another gifted athlete, possibly the strongest woman ever to play top-level tennis -- reached the pinnacle in 1979 with an explosive, relentlessly aggressive serve-volley attack. Briefly, the vogue was for all the aspiring players to rush the net, whether they were equipped to do so or not.

Tracy Austin, a kind of Evert clone, won the 1979 U.S. Open at age 16 and the future promptly was bequeathed to her. Now Jaeger and Mandlikova -- vastly different in build, style, and temperament, but each versatile and capable of playing an all-court game -- are challenging for supremacy much more quickly than anyone had imagined.

Evert reflected on this recently when she was asked to peer into the future and, discounting her 12-year-old sister, Clare, and other juvenile prodigies, predict how the tennis rankings will look in five years.

"I have a lot of respect for Andrea's game. I think she can do everything," Evert said. "Right now she doesn't have the physique to play serve-volley. Like Tracy and me, she's not physically suited to play that type of game and overpower people the way Martina and Hana can. But when she grows, I think Andrea will have it all.

"She's already shown a flair for volleying, she has a great first serve, she moves like a dream and mentally she's strong. I would have put my money on her in two or three years. I think Hana has it all physically, but I'm still not convinced that she's a champion mentally."

Mandlikova has made believers of most colleagues in the past five months, appearing to have overcome her tendency to play a set or so of dazzling tennis, then disintegrate before closing out a match. No one doubts she has extraordinary talent: exquisite quickness, reflexes, racket control and touch. But Evert wonders if she ever will shed the inconsistency.

"I don't think she's completely over it. I think she's made a breakthrough and can finish matches a lot better now, but I think there will always be that little element of unpredictability. It's just part of her personality, and it will make her a flashy player -- smetimes brilliant, sometimes careless. She loves to take risks and trying daring shots, and that leaves her little margin for error."

Much the same could be, and has been, said of Navratilova.

What about Austin?

"I think Tracy and I are a lot alike," Evert said.

"I would compare us, in our mental approach and our styles, more than any other two players. If Tracy isn't the dominant player the next couple of years, I don't think any baseliner who'll come along in the next five or 10 years. I think that players will develop all-court games in the future. I think Andrea and Hana are setting the trend now."

Perhaps somebody we haven't heard of yet will be on top in five years. Most likely Jaeger, Mandlikova and Austin will be in the fight, and Navratilova, now 24, fully expects to be around then.

"There are so many kinds coming along, you can't project," said Billie Jean King, the matriarch of women's pro tennis, who 10 years ago foresaw the boom now upon us. "Chris and Evonne made their mark in 1971, Andrea and Hana came along in 1980. They'll be around for awhile, if they want it. But they'll have to keep working, because the whole level of women's tennis is rising.

"The women hit the ball harder, and can do more with it, every year. There is better coaching, better equipment, more knowledge about training and technique and biomechanics. We've just scratched the surface, and the process of evolution is speeding up. And there's much more incentive now for a good athlete to take up tennis. Tracy is a millionaire at 18, and kids see that. When I was 18, I hadn't earned a penny. I don't know that any one style will be predominant, but everybody is playing more 'athletic' tennis than before."

Navratilova agrees. Taking her cue from Jaeger, she shot a few hoops yesterday morning before practice.

"I think you'll still see different styles, baseliners and net-rushers and all-court players, because that reflects people's personalities," she said. "It's not in Chris' or Tracy's nature to come to the net, or in mine to stay at the baseline, even if we could play that game. But Andrea and Hana are "jocks" whereas Chris and Tracy played only tennis. I think you'll see more good athletes playing tennis in the future."

You can bet your $160 Price graphite racket you will.