If the world of women's tennis is 16-year-old Tracy Austin's oyster, as it now appears, then surely she is its cultured pearl -- cultivated for years in a controlled environment just right for growth, now polished into something precious.

Austin's dazzling victory yesterday in the $120,000 Avon Championships of Washington was her third in three tournaments since turning professional in October. By thrashing Wimbledon champion Martina Navratilova, 6-3, 6-2, she collected $24,000, increasing her winnings in just under four months as a pro to more than $70,000.

Precious, indeed.

But if you have the misfortune of being across the net from this pearl, she can cause as much discomfort as a bad oyster, as Navratilova learned for the third time in 10 months.

At the start, the 22-year-old expatriate Czech left-hander, who had won the Washington stop on the women's tour three of the last four years, was so nervous that she was gulping Maalox to settle her stomach. The way she was playing -- serving poorly, terribly erratic on her ground strokes, particularly the backhand -- she had reason to feel queasy.

By the time Austin served out the first set in a crucial game, coming back from 15-40 to hold after two deuces, Navratilova looked as if she needed something stronger. And by the end of the 64-minute match, she looked just ghastly, as if trying to digest a half-dozen raw Blue Points, shells and all.

After her decisive semifinal victory over Australian Dianne Fromholtz, Navratilova said she finds it hard to get psyched up to play Austin the way she does for arch rival Chris Evert, whose unerring back-court game Austin's so resembles.

This seemed curious, for it was Austin who terminated Navratilova's prized 37-match winning streak in Dallas last March -- on the final point of a sudden death tie breaker, no less -- after the bouncy Czech had monopolized the first seven tournaments of the 1978 winter tour.

And Austin had humiliated a weary and disinterested Navratilova, 6-1, 6-1, in their last meeting, at Tokyo in November. That made their career rivalry 5-2, after Navratilova had won their first three encounters in routs.

Yesterday, after Austin sickened her with steadiness and left her woozy from an overdose of passing shots, Navratilova adopted a different theme.

"I know I have to be at the top of my game to beat Tracy because she has become really tough, really good. I know when I don't play my best, I can't win," she told the sellout crowd of 5,000 at George Washington University's Smith Center during the presentation ceremonies.

"I was 'up' today," she added in a postmatch press conference, explaining that she went to friend-manager Sandra Haynie for the Maalox bottle at changeovers in the first set, and didn't even sit down because she wanted to burn up excess nervous energy.

"I was up for the finals and it didn't really matter who I was going to play. Mentally, I was okay. But my game wasn't up. I just haven't had enough play the last few weeks to be really tough," she said.

Navratilova was bedridden with flu the week before coming to Washington, which curtailed the intensive practive and conditioning routine she had planned to get herself into the same peak shape she attained before the start of last season.

She seemed to find her timing gradually as she overpowered Lea Antonoplis, Ruta Gerulaitis, Ann Kiyomura and Fromholtz to reach the final without losing a set, but yesterday she "just couldn't find it," as the tennins players say when their touch and timing evaporate, and Austin is just the sort of human thrashing machine to take full advantage of an opponent's off day.

Pam Shriver, Princess Pearl's great teen rival from Lutherville, Md., foresaw this possibility. After her 6-3, 1-6, 6-1 loss to Austin in the quarterfinals -- the only one of five matches in which Austin lost more than five games -- Shriver assessed the probable Navratilova-Austin matchup this way:

"I think it just depends on Martina, because she's the variable. I think Tracy will play pretty much the way she's been playing, but Martina can either be incredibly strong or she can have one of those days that she kind of falls apart. But heck, I wouldn't want to bet against Tracy in the finals."

Shriver couldn't have been more on the money. Navratilova started to unravel in the very first game, overhitting two returns of the weak Austin second serves she wanted to exploit. She lost her serve at love in the second game, double-faulting on the first point, missing three of four first serves, and muffing two volleys around a blistering forehand cross-court winner by Austin.

"I had problems with everything, my first serve, the forehand when I tried to hit out on it at the beginning of the match, then the backhand approach shots that I very rarely miss," Navratilova moaned later. "None of my strengths were working.

"I started trying to figure out, technically, what was wrong with my backhand, but you can't do that in the middle of a match... You don't get too many openings against Tracy, so you have to take advantage of them. But when I had the opportunity to get in to the net and get her out of position, I messed up the approach shots."

Austin, meanwhile, was again the Grim Reaper of the back court, the strokes of her racket as deadly as Lizzie Borden's 40 whacks. Her steadiness had Navratilova muttering to herself continuously and impatiently rushing into errors. At the end of one long rally, Martina was so exasperated she exclaimed: "It's so boring, I can't stand it."

While Navratilova seemed to be hitting late on every backhand down the line, floating the ball long when she tried a sliced approach from that side or hammering it into the net when she tried to come over the ball, Austin was always in position, making few unforced errors.

This peral's setting is a 24-karat ground game, and she has a golden gift of court sense. She knows the dimensions of the white-lined carpet, and used every inch of it yesterday.

She kept Navratilova pinned back in uncomfortable territory with the consistent depth of her shots, scrambled so well that she got to bals you would swear she could not reach, and lobbed as if she had built-in rader. On until Austin was serving for the match. She got to 5-2, 30-0 by wining 10 points in a row, but Navratilova saved a match point at 40-30 and got to advantage. Austin canceled it with a blistering backhand cross-court winner, and then Navratilova hit an easy overhead wide and knocked another dreadful backhand long -- an appropriate final point, mirroring so many earlier ones.

Top-seeded Mima Jausovec, 22, and Virginia Ruzici, 23, split $14,000 for their 4-6, 6-2, 6-4 victory over Sharon Walsh, 26, and Renee Richards, 43, in the doubles final. Obviously women's tennis today is a young person's game.

Austin will be back in class today at Polling Hills (Calif.) High, where she is a sophomore. These days this blond, blue-eyed, 5-foot-3, 110-pound pearl spends two weeks at a time in school, and then two in the high-pressure, competitive world that is her oyster. four important points in the second set, lobs to within inches of the baseline either went for outright winners or set her up for the kill.

Austin had only three break points against her in the amtch. Two of those came with her serving at 5-3 in the first set. Navratilova sailed a backhand long on the first, and then Austin drove her wide with two forehand cross-court shots on the sideline and came in for a forehand volley winner down the line on the second.

The third break point did not come year-old Fleming during a nervous start until the 6-foot-5 New Jersey player found his form.

Surprisingly it was 32-year-old Nastase who turned out to be the weak link, losing five of his eight service games.

Stewart, who rushed from Melbourne to London Wednesday to come in as a last-minute replacepent partner for the Romanian, played solidly.