Coolly and deliberately, Rodney Harmon adjusted his blue cap more snugly over his short black hair, long, spindly fingers searching for some perspiration in the 99-degree heat, then trying swat away the annoying gnats that flew nonstop in the stillness of the yellow tent.

Harmon had just survived the second round of the $200,000 D.C. National Bank Classic. He hadn't wanted to disappoint his grandmother and friends who had driven more than 100 miles from his hometown in Richmond. The 2-6, 7-6 (10-8), 7-6 (8-6) victory over Cassio Motta, in his fifth pro tournament, was perhaps his biggest scare.

That's all right with him, though. For Harmon, a graduate of Southern Methodist University, still needs an education.

"I'm just maturing as a person," said Harmon, 21. "I'm learning what I need to know." Harmon has been a professional for all of two months, starting on the grass in Beckingham at the end of May, continuing on through Wimbledon, where he reached the third round.

"Going to England was good, because the mistakes I made there helped me here. I learned a lot about competing, a lot about guts and fighting. Today, I fought and won."

It was the night schedule that was the loser yesterday; it was postponed as the rains came down at 7:45, interrupting the feature match between No. 1 seed Jose-Luis Clerc and Eddie Dibbs. The match has been rescheduled for tonight at 7.

Second-round action continues with No. 2 seed Jimmy Arias playing the second match of the afternoon on the stadium court, to be followed by Mel Purcell against Diego Perez.

Harmon will play Claudio Panatta after the Clerc-Dibbs match.

Clerc, now ranked ninth in the world, had broken Dibbs' serve in the first game. The second game was tied at 15-all. The match between Ramesh Krishnan and Mario Martinez was also interrupted, with Martinez leading, 6-7, 6-2, 2-0.

In his day match, Harmon was down, 6-5, in the third-set tie breaker when Motta sent a forehand down the right base line. Harmon was on the left.

Harmon raced over, stretched out his lean 6-foot-2 body and plopped the ball skyward. It landed in.

Motta netted the ball on his smash and hung his head for many seconds. afterward. Harmon swept the next two points for the match.

The crowd of 2,800 roared, Harmon yelled and Motta cringed.

"I don't know how I got it, but I got it. Fate . . . I guess," a breathless Harmon said.

"He was a bit nervous," said his coach of 11 years, Willis Thomas. "He likes to play here so much."

Maybe too much?

Thomas smiled.

Harmon first burst out of the Texas sun last September in the U.S. Open, reaching the quarterfinals, beating Eliot Teltscher along the way. His opponent: Jimmy Connors.

Harmon turned to Arthur Ashe for advice. Harmon lost in straight sets.

Thomas frowned slightly. "He listens to whatever you say. That may have been the problem at the Open. He was a little mixed up how he was going to play. A victim of too much advice. Now, with me, he'll find a set style of play."

Harmon's style is serve and volley, not especially well-suited to the slow, green clay at Rock Creek Stadium, traditionally a tournament where a Clerc or Vilas dominates. Still, Harmon reached the quarterfinals last year.

"He's ready to win here, especially because of the lack of names," Thomas said.

The partisan crowd certainly wanted Harmon to win. "It's good when the crowd gets in the match. Lots of times I don't hear them. But when I really hear it, it's good."

Harmon appears poised and personable, and is extremely gregarious. Nothing appears to faze him. He's ready to do some growing.

"I wanted to graduate badly. Now I'm ready to totally devote myself to tennis," said Harmon, ranked 61st in the world and the 14th seed here.

The sweating for the tournament was temporarily abated. "I felt like I was out there a long time. You should have seen how much water I drank in the locker room."

Harmon had been practicing every day for two hours, running three miles in the noonday heat, preparing for the Classic. "I like to sweat," he said grinning.

Rodney Harmon, like most, enjoys winning, too.

Brian Gottfried, the third seed, said yesterday he has been offered guarantee money at a Grand Prix tournament, but that he turned down the offer.

"I never accepted it," Gottfried said after defeating Tom Cain, 3-6, 6-2, 6-4. "I hope the top players don't revolt. They need the game as much as the game needs them."