Pam Shriver is a lot like her hair: irrepressible, a bit unruly, lovely to look at. In a recent issue of a national sports magazine, a prominent sportswriter wrote that she was "a positively stunning young woman."

She is sitting at breakfast, wearing sweats and a grin. "I was amazed it took someone that long to write it," she says.

The awkwardness is gone. Shriver is filling out her potential and her game. As her sister said, "Now you fit your shoe size."

Both feet, Shriver says, are finally "planted firmly on the ground. Before? One might have touched momentarily. One might have been on the moon."

At 19, she is comfortable being herself. It shows.

Shriver, who is seeded fifth in the Avon Championships of Washington, finished 1980 ranked 12th in the world and moved up to seventh by the end of 1981 (winning 71 percent of her matches). That is no mean jump, even for someone nearly 6 feet tall.

She is "riding a wave" (and her serve) that overwhelmed Pam Casale last night, 6-1, 6-2. "I'm hiding in the tube," she said, smiling. "No one can see me."

Not for long. By the end of 1982, she should be "rocking the boat" of Nos. 1, 2 and 3, said her coach, Don Candy.

For some time, she was rocking only her own boat. It began in 1978, when she startled everyone by beating Martina Navratilova in the semifinals of the U.S. Open and then extending Chris Evert Lloyd to 7-5, 6-4 in the final. This can do strange things to a young mind, especially if the young mind goes right back to school, losing the chance to develop the match toughness needed to maintain that level.

"At the U.S. Open, everyone said, 'Here's the next Margaret Court, she'll be No. 1 in three years.' It's not like I listened but I knew what was expected," Shriver said. "When I made the finals, it wasn't like a fluke, but a flash of what I could be. I wasn't gonna be consistent for a while. It just jelled for two weeks and I had to live with what everyone was saying. When I went out on the court, I would think, 'What will they write if I lose?' "

In the spring of 1979, after turning pro, she injured her right shoulder, and had to withdraw from Wimbledon. The anguish of not being able to do what she and others expected was compounded by the physical anguish of trying to play.

"I was probably a bit neurotic," she says, "a bit petulant."

Tour referee Lee Jackson says, "There are those that just stand there like puppets, marionettes, and just hit the tennis ball."

Shriver is not one of those. "There are 100 things going on in her head," Jackson said. "Maybe an unintelligent person just hits the ball back and forth. Their path is narrow. Pam's is broad. On the court, she has to narrow it and she doesn't know how."

She is learning. Shriver, who beat Austin in the quarterfinals of Wimbledon, had a much publicized brouhaha with her in Toronto, when she lost in the semifinals and cursed Austin in the process. Part of her charm is that she says pretty much what she's thinking when she's thinking it. But, she is learning that isn't always a great idea.

The two played each other next in the quarterfinals of the Australian Open. Shriver won, 7-5, 7-6, and how she did it mattered most.

Austin was serving at 2-3 in the tie breaker. She hit a lob and Shriver, thinking it was surely out, let it go. The umpire called it good. "Instead of 4-2 mine," Shriver said, "it was 3-3. I asked the official judge, 'Did you see it? He said, 'Yes, the ball is good.' I won four of the next five points (two on unreturnable serves). In the past I would have been so hacked off, I would have just blown it and lost, 6-3. Slowly, but surely, you get sick of blowing it for yourself."

Shriver tells a story about when she was 5, hitting against a backboard. The ball, the only one she had, got caught in a mesh fence atop the backboard. She shook the fence and nothing happened. Finally, she had no choice. She climbed the 10-foot high fence, inched her way over to the ball, grabbed the ball and promptly fell onto the cement. "That's the way I am," she says. "That's the way I was with tennis."

She says she is "not as tied up around it (the No. 1 ranking)" as she used to be. "I was too messed up at age 17 to be ranked No. 7," she said. "I don't think I would have been able to put up with the pressure of being No. 1 at that age. I don't think I could put up with the pressure of being (No.) 1 or 2 now. Maybe in a couple of years.

"I can remember thinking at age 16 to be ranked 12, there was a lot of pressure. I was thinking, 'My God, if it's like this now, what's it like higher?' It caused a bit of mixed emotions. I knew I was capable of it. I was supposed to want it and I wasn't sure. Young as I was, it was scary."

Shriver is sure of this much: "Pressures are something you can grow into, too."

Before, she said, "I knew what I was capable of but I wasn't letting go enough to let it happen."

Watching it happen is a joy.