The man in the red sweater approached with glad tidings. "Hey, guess what?" he said. "I just found out. Bill Tilden won his first U.S. Open at 27."

"So," said Bjorn Borg, who has won everything in tennis but the U.S. Open, "there's still time."

He smiled the smile you never saw when he was engaged in the pursuit of that elusive goal. He is 27 now and seven months into his early retirement. There are no cracks in the resolve, only in the once implacable demeanor.

"For sure," he said, laughing. Some things are still instinctive.

There is something disconcerting about an athlete who quits young and on top, especially one who says it just isn't fun any more. Perhaps it's the idea of being able to choose not to do something the rest of us would kill for. So, wherever Borg goes, people think, "How dare he? The rest of us have to work."

Wherever Borg goes, there are people thinking this is a temporary aberration in behavior. "He'll get over it," they say. "He'll go back. He'll want it again."

There is nothing in his smile to suggest this is so. "The people are so used to seeing an athlete playing, they cannot accept him going away," Borg said before tonight's exhibition at the Civic Center with Roscoe Tanner.

When Borg announced his decision in January to retire from competitive tennis, some said it was because his wife Mariana wanted him to do it.

"That was never true," he said. "A lot of people say, 'Why do I quit tennis? There has to be a reason.' It can't be that I don't enjoy tennis. It must be Mariana who doesn't like me to play tennis. I was the one who told her, 'I'm going to retire.' She didn't believe me. I told her the first time, she said, 'Don't joke.' "

There were stories she was ill. "She is fine," he said. "She had kidney stones. They said she had cancer, that she was dying. Not pleasant things."

Their life has changed, which is what he wanted. "It's so much more relaxed," he said. "When I was playing, Mariana was always nervous because she wanted the best for me. And I was nervous. Pressure. Always pressure.

"If I was getting mad, she was the one who got all the bad feelings from me. When I came home to the hotel room, there was no way to keep it inside. I could but I didn't show my feelings here."

Meaning on court.

"You mean you showed your feelings?" someone asked.

"Only twice a year," he said, wryly. "In spring and winter."

His feelings about tennis seem clear. An exhibition here and there is fine. Next week, he will play in a mixed doubles event with Bettina Bunge against, among others, Chris Evert Lloyd and Jimmy Connors and John Lloyd and Wendy Turnbull. That's fun. The rest isn't. "If I could be the No. 1 player and just play the French, the U.S. Open and Wimbledon, it would be fine," he said. "But it doesn't exist that way."

Last August, he spent a week at Vitis Gerulaitis' house on Long Island, helping him prepare for the U.S. Open. Word was that Gerulaitis didn't win a set. "Well," he said, "I play pretty good in practice. Not too bad but it doesn't change anything."

There will be no French, no Wimbledon, no U.S. Open for Borg in 1984. "No, no, and no," he said.

He may enter a minor tournament or two, he says. "Right now, I have no idea what tournament that would be or if I want to do it or if I have the time to do it," he said. He is busy with a new line of clothing and a new Bjorn Borg sports center in Sweden.

"If I played, it would be the smallest Grand Prix tournament," he said. "I would do it for myself, if it would be fun. I'm not going to prove anything."But inevitably "it would become a big thing. And then maybe I would have to play more tournaments."

He rolled his eyes and smiled. As it is, "If I say maybe I'll play a few tournaments, the next day there are big headlines, 'Big comeback.' I'm not going to make a comeback."

If that is so, it may be, in part, because of the consuming way he plays the game. "I have to be 100 percent serious," he said.

Which leaves no room for that smile. But his way also left no room for doubt. "I don't regret anything," he said. "I don't miss anything because I know I did what I had to do."

For sure.