At 6 p.m. Friday Eric Korita, a qualifier who plays fifth on the Southern Methodist University tennis team, learned he would be playing on the stadium court against Yannick Noah, the ninth seeded player in the U.S. Open.

"I was shaking for about an hour," said Korita, who took Noah five nail-biting sets before losing today's third-round match. "I was really nervous. I was calling everybody. I have never experienced anything like this before. I was lucky someone had asked me to hit the day before on the stadium court and I tried to get used to it."

Korita is 19 and ranked 335th in the world. Noah is 22 and ranked 10th in the world. Near the end of the match, with the two men tied at two sets apiece and four games all, it was Noah's turn to be nervous. He tried to relax, to breathe deeply. "A match like this, you play four hours, and that's it," he said.

It all came down to one point, a break point with Noah serving at 30-40.

Korita said, "When I broke at 4-2 to make it 4-3 and held serve and then I had a break point (at 4), I said, 'I have to stand back and just go for it.' If I could hit it, then I could hold my serve (and close out the match). And I was that close. Close doesn't really count that much."

Korita's return sailed long. When Noah broke Korita's serve in the next game, to win, 7-5, 6-7 (7-3), 6-4, 3-6, 6-4, Noah finally took that deep breath. "His serve was the best serve I've ever played against," Noah said. "It was a very close match. He just missed two or three easy volleys. That was the difference."

The difference between the top 10 and a qualifier?

Although Noah's serve was broken only twice in the match (in the fourth and fifth sets), Korita was tenacious. Down two points in the second set tiebreaker, he won six points in a row -- a meaningless streak to a man who once ate 26 hot dogs in a day.

In the fourth set, he took a 3-0 lead, which he never lost, and forced Noah to a fifth and deciding set, which proved the difference between the qualifier and the top 10 player.

Noah smiled. "They are better than the guys in the main draw," he said.

Noah speaks from experience. Last year, he had to go five sets in the first round with a qualifier named Andy Andrews. Noah, a jaded veteran who ended Ivan Lendl's 44-match winning streak this spring and then beat him again to win the Davis Cup for France this summer, said, "When I was younger, I wasn't very nervous about playing on the stadium court because you have nothing to lose. You don't have any pressure on you. I knew how it was and the pressure is there and it's very difficult because I was the seed. I was very nervous."

There were no other Cinderalla stories at the Open today. All the seeded players did what was expected of them and with dispatch.

Martina Navratilova, No. 1 seed , playing with elan, beat Nancy Yeargin, 6-3, 6-3. Such is Navratilova's confidence now that it begs the question: How will she react emotionally if she loses?

Navratilova paused thoughtfully. "That's a good question," she said.

Tracy Austin, No. 3, beat Jo Durie, 6-4, 6-3. Pam Shriver, No. 7, of Lutherville, Md., beat Dana Gilbert, 3-6, 6-2, 6-3, 6-1, and Hana Mandlikova, No. 5, defeated Manuela Maleeva, 7-6 (7-4), 6-2.

Among the men, Lendl, No. 3, who struggled so against Tim Mayotte Friday night, had an easy afternoon, beating Harold Solomon, 6-3, 6-0, 6-1.

For the second day in a row there was a record-setting crowd, as 20,792 people got to see one of the nicest tennis phenomena--a young player who literally comes out of nowhere (in Korita's case, Glenville, Ill.) to give a top player a fright. "I was really scared," Noah said.

Noah knew so little about Korita that midway through the press conference, he had to ask his first name. "People said, 'Who do you play?' and I said, 'Korita.' They said, 'Oh, big serve.' That's what I knew about him."

Korita, who had 16 aces in his previous match, had eight today. His serve is difficult to read, Noah said, "because it is faster and you never know where he is going to go. Four or five times, it almost hit me."

Korita talked to his coaches Dennis Ralston and Nick Boleteri and to player Brian Gottfried. "I asked them what he does," he said. "I have watched him on television and never thought about playing him."

"I felt his backhand was better than his forehand," he said. "I was going to try to attack his forehand."

But at the end, it was Noah's forehand that proved the difference. Korita fell behind, 15-40, on his serve, missing a forehand volley, and netting a backhand approach shot.

He saved two match points with lovely volleys. But two forehand cross-court passing shots gave Noah the game and the match.

Korita's best previous performance was a win in a satellite tournament this summer. He was a quarterfinalist in the 1981 Wimbledon junior championship and ranked fifth in the U.S. among players 18 and under the same year. Such credentials do not usually lead to the stadium court at the U.S. Open a year later.

But there has been a big change in Korita, who is 6-foot-5 and wears size 15 shoes. "In the last five or six months I have lost about 39 pounds and that helped me," he said. "I've always had to be pushed and I wanted to do it and I thought I had to do it."

He now weighs 198. "I cut on down on a lot of Cokes and greasy food," he said.

Perhaps someday soon he'll be a heavyweight in the game.