A radio man was persistent. He put the microphone in Tracy Austin's face. For the people in radioland, he commanded the young woman, "Tell us what elements of your game are the best." Tracy Austin told the radio guy where to get off.

"My whole game is what I concentrate on," she said. This was minutes after she defeated Pam Shriver, 6-3, 1-6, 6-1, in the quarterfinals of the $125,000 Avon tennis tournament at Smith Center last night. Even a radio guy might have noticed Austin's completeness.

"But..." the radioite began.

"Not any one point," Austin said, and an innocent bystander suddenly realized the young player was more, much more, than her sunny yellow dress and little pigtails suggest.

A killer in pigtails.

Shriver-Austin will be a continuing rivalry in women's tennis. Last night's go was their 10th, all won by Austin, but in a sense it was the first, for only now are both players fully accepted as world class. At 16, they are princesses-in-impatient-waiting.

Three years hence, maybe five at most, they will ascend to the throne yelded up, reluctantly but inevitably, by Chris Evert and Martina Navrotilova, Evonne Goolagong and Virginia Wade. Already Austin is catalogued as one of six "AA" players on the Avon Circuit -- the sponsors who put up the most money are guaranteed the presence of the most "AA" players -- and Shriver is one of seven "A" players.

Austin is a professional now, having fled the amateurs at 15 last October. She's doing her schoolwork between lobs. Shriver, hurrying to catch up with all that loot (Avon offers $2.2 million in its three-month circuit this winter), is finishing her last two years of high school in one year. She graduates this summer.

"We're both young," Shriver said, trying to answer a newspaperman's silly question. The question (with a blush) was: Do you imagine you'll be playing Austin forever?

"And we're both pretty good."

This girl is wonderful at understatement.

"So I guess we'll be playing sometime guile.

Shriver is 6 feet tall and plays the big game, expldoing serves that go invisible and rushing the net to crash volleys into hiding. Austin, a tiny thing at 5-4 and 110, has a serve that, to the ear, sounds like a marshmallow being beaten with a feather duster. But every shot in her repertoire -- she has a "whole game," remember -- is a buided missile.

They sold all the tickets last night, some 5,000, and for the first time ever Austin could hear a single voice in the crowd. "One guy was hollering for me," she said. "Tell him, 'I love you.'" She could hear one fellow because, in the course of human nature, most of the paying customers swooned over Shriver, who lives 50 miles from Smith Center in Lutherville, Md.

Austin was the world's sweetheart when she took her pigtails onto Centre Court at Wimbledon two years ago against Queen Evert. And the resulting display of affection for Shriver was a new, and very loud, experience for Austin.

She remembered playing Navratilova in front of 10,000 people a year ago in Dallas. That is Navratilova's hometown now. "I was the underdog then, so about half the people were for me, and half were for Martina," Austin sadi. Virtually everyone was for Shriver here.

"I'm kinda the darling of the area," Shriver said disarmingly. "I guess they think I'm kinda cute."

Three months ago, Shriver became the youngest finalist in woman's U.S. Open history. Until this week, she hadn't played in another tournament. She wasn't "tournament tough," she said. "I've had a lot of things on my mind besides tennis."

Austin, hearting that, said, "A boyfriend?"

Shriver giggled. "Not a boyfriend."

Books and grades and things. Shriver meant. Everyone knew, of course, she was reminidng them that Austin, on tour, is thinking of little besides the game. There's a message here, delivered subtly by a 16-year-old: another day, and a better one to boot, will come.

Even the cheering might have worked against her, Shriver admitted. It was nice to hear, but adulation becomes distraction, and pressure, too.

"The crowd, even though it's for you, sometimes can get you uptight a litte," Shriver said. "So many people were calling up home, wanting tickets, all my friends and that. It's not that easy when you have everybody you know around and they're saying, 'Go, Pam, go, we want you to win.'

"It can root you on at one time, and the next time it can you all uptight."

Shriver was visibly bothered, often mssing easy shots, especially early on. But if Austin ever wobbled, no one much noticed. And when Shriver fell from excellence late, Austin rushed in for that 6-1 execution. Is that, someone asked, her killer instinct at work? If so, it didn't show through the pigtails.

"Because it doesn't show doesn't mean you don't have it," Austin said. "Down deep, I have it."