Tony Arias sat in the stands at Rock Creek Stadium trying to sound stern. "I think he peaked at 12," he said, watching his son the tennis player, who is 18 and ranked 11th in the world.

"Aw," Jimmy Arias said later, "he always says that."

One day, when Jimmy Arias was 12, Rod Laver came to town. Arias, who grew up near Buffalo, N.Y., was the U.S. 12-and-under champion. Laver was a two-time Grand Slam winner.

"They called Jimmy to practice with him," Tony Arias said. "All the people said, 'We want a set. We want a set.'

"So they played a set. Laver had to struggle to win, 7-5. That's how good he was when he was 12," he said, the sternness wilting in the heat yesterday.

"I just remember I probably played as well that match as I could play right now," his son said after beating John Mattke, 6-2, 6-4, in 63 minutes in the D.C. National Bank Classic. "It was almost scary. I was serving and volleying and serving aces. I was doing things I can't do now. I almost won.

"It was 2-0, mine. He holds up the balls and says, 'You're not going to win another game.' I'm kind of psyched out so I don't play that well for the next three games and he's up, 3-2," Arias said.

"Then I start playing great again and I get it to 5-all. He holds. At 6-5, I've been serving so hard, I like threw my shoulder out. I just couldn't serve anymore. I lost it on a deuce game."

He glanced at his father. "You said, 'You played fair; you lost, though.' "

"No," his father said. "I said, 'You played good.' "

"Two years later you said, 'You played good,' " the son replied.

And what did Laver say? "He said, 'It's much too early to tell whether he's going to be any good,' " Tony Arias said, a hint of vindication.

It is no longer too early to tell about Jimmy Arias, who is the No. 2 seed here. That set against Rod Laver six years ago may have given Arias an insight into his future, but it was a semifinal match here last year against Jose-Luis Clerc that told him the future was now. The newspaper clippings are home framed on the wall; the memory he keeps with him. Arias was unseeded, ranked 79th in the world. Clerc had won two consecutive tournaments and was ranked fifth.

Arias beat him with a forehand that, he says, is pretty violent; a willingness to chase down every possibility and a little wood shot that gave him match point.

"I remember talking to somebody at the beginning of the week and saying, 'I always win my first-round match but I never get any further. If I can just get one big tournament, one big week, then I'll be all set. I won't choke against the big names.' As soon as I won it, I said, 'This is it.' "

He reached the finals of the U.S. Open Clay Courts, gave Jimmy Connors a tough four-set match at the U.S. Open and then won his first Grand Prix tournament in Tokyo.

He was also experimenting with a new midsize racket, thanks to a new contract with Donnay. He had been playing with a standard size Wilson since he was 5. The new racket, which he used in two tournaments, helped his serve and his volley, he said.

"It was much against his father's and my wishes," said his coach, Nick Bollettieri. "He had to try to adjust his swing to his racket. Mr. Arias spent years to develop his racket to his swing. There were four months of complete chaos. He was down in the dumps, discouraged."

Confidence was never something Arias lacked. "He was not humble," his father said (though his son often vomited before matches). He asked Bollettieri to come to Italy. "He's great for my confidence," Arias said.

"In a way, he's the opposite of Dad. Dad tells me all the things I'm doing wrong. Nick tells me what I'm doing right. I've got the perfect group there."

He won Florence and then the Italian Open with renewed confidence and a bit of luck (Clerc was defaulted from their quarterfinal match because he had walked off the court during a doubles match).

He went to Paris and took a cab with two women players, heading for dinner on the Champs Elysees. "I decided I'd be a nice guy and pay," he said. "I went to pay and the driver said he didn't have change for 100 (francs). I said, 'That's all I've got.' He said something in French. This dog that was sitting in the front jumped and ripped into my arm."

Arias was wearing a new leather jacket he had bought in Italy. "The teeth made it through."

Without the jacket, he said, smiling, "I'd be a lefty."

It wasn't the only injury he got in Paris. He lost to Guillermo Vilas in the fourth round of the French Open, playing with a pulled stomach muscle that he hurt in the second round. The injury forced him to withdraw from Wimbledon.

Although he says the injury didn't hurt last week when he lost in the final in Boston to Clerc, it was bothering him yesterday. All but a few of his serves today were "slow poopers." He iced it and had ultrasound treatments after the match.

His father says Arias doesn't work as hard as he used to. Eric Korita, who also trains with Bollettieri and grew up playing against him, said, "He hates to lose. He never tanks a set in practice."

"I don't understand why everyone's not like that," Arias said. "My little brother who plays tennis, he just wants to have fun. I say, 'How can you just want to have fun? Don't you want to be the best?' "

Arias' father, who taught him everything he could before sending him to Bollettieri at age 13, sat listening, proudly. "I am not here to praise you," he said.

"I know," his son said, smiling.