Beneath sullen skies, John Patrick McEnroe Jr., the No. 1-ranked tennis player in the world, stepped onto the stadium court at the National Tennis Center Tuesday to play his first match in the U.S. Open, where he is the two-time defending champion.

Within 20 minutes, many in the crowd of 15,000, his countrymen and his fellow New Yorkers, were hooting at him and cheering wildly for a Chilean player, Juan Nunez, most had never heard of until he stepped onto the court with McEnroe.

"It was," McEnroe said later, "quite disappointing."

But not surprising. McEnroe knows that wherever he goes in the world, he will face a similar reaction. He is tennis' public enemy No. 1, and that is not a label he relishes, especially here, in a stadium six miles from where he grew up and still lives.

The label has tempered much of the joy McEnroe would ordinarily be feeling. He has ascended to the heights he dreamed of as a boy. At 22, he is the Wimbledon and U.S. Open champion, at the moment the dominant figure in the game.

And yet, as he sat Thursday night sullenly answering another stream of questions about the latest controversy swirling around him -- the $5,000 fine levied by the Men's International Professional Tennis Council -- he looked like a very unhappy young man.

McEnroe is tennis' tortured genius. On court, he is a gifted, gutsy player. Many of his qualities are heroic. He has proven repeatedly that he is as courageous a competitor as there is in sport today.

But there is one major flaw: he cannot, will not, accept and adjust to what he considers a bad call on the court; he refuses to back off from an argument. He is driven to make his point, then make it again and again, usually rudely.

Thursday night, while he was manhandling Tom Gullikson, McEnroe got what looked to be a bad call on a Gullikson backhand down the line. McEnroe stopped and stared. He asked the umpire if he thought the call was correct. He shook his head, then took a ball and placed it where he thought it had landed -- in the doubles court.

Then he played. And won the game. Yet, during the changeover, McEnroe was still complaining about the call, a matter now completely moot. An injustice had been done and McEnroe was outraged.

He was probably correct about the call. Tennis people will tell you that most of the time when McEnroe argues a call he is right because he has such excellent eyesight. He will also argue if he sees a call go his way that he thinks is wrong.

He rarely uses obscenity on the court and has rarely made the obscene gestures made famous by Ilie Nastase and Jimmy Connors. In an era when Connors went four years without playing a Davis Cup match and when Bjorn Borg no longer plays Davis Cup because it doesn't interest him, McEnroe has always played when asked. He carries his Davis Cup jacket around like a security blanket.

He has turned down a flat $1 million to play in South Africa because of the government's policy of apartheid. He is loyal to his friends and nice to children who seek his autograph.

McEnroe says he does not want to be disliked. He says he would like to change his image, but is bright enough to realize it will now be terribly difficult to accomplish that.

"It is disappointing, very frustrating, to get this (hooting, catcalling and booing) here," McEnroe said. "I really don't need that. But I have to get used to it. The first time I even sniff at a call, they (the fans) start giving me a hard time.

"I know I'm going to have to deal with that for a while -- six months, maybe longer. But what it all gets down to is that you play for yourself. I don't need extra reasons to try to win. I dreamed about winning this tournament as a boy and the enjoyment I get from winning has nothing to do with the fans, the umpires, the media, anyone.

"That doesn't mean I go around wanting to win just to spite people, I don't need to do that. Spite has nothing to do with it."

The latest storm surrounding McEnroe is a recycled one. It dates back to his epic two weeks at Wimbledon where he fought nonstop with officials, breaking off his arguments just long enough to play brilliantly and win the tournament.

Now, the fine has been announced, by happenstance on the same day McEnroe played Gullikson, the player he was facing when his troubles began at Wimbledon.

McEnroe says the fine and the timing of the announcement were unfair. He doesn't want to discuss it during the tournament and has turned the entire matter over to his father and leading defender, attorney John P. McEnroe Sr.

"No matter how well John plays people only talk about the couple of minutes when he is arguing," McEnroe's father said recently. "They don't talk about how well he played."

They also root fiercely against McEnroe. Part of that is because McEnroe is the overdog now. His play and his pouting rarely inspire sympathy. But there are moments.

Last year, in his superb four-hour semifinal here with Jimmy Connors, McEnroe lost the third set, 6-0, to go down, two sets to one. He was arguing with linesman, the umpire and tournament referee Mike Blanchard. He tossed his racket in frustration at one point and almost nailed Connors. He looked finished.

And then, he regrouped. Slowly, he dug in and fought his way back into the match. The crowd, solidly behind Connors to that point, seemed to swing, admiring the grit of McEnroe.

"All these people want to see is two guys out there trying to kill each other," Connors said. "They know when John and I play they're going to see that. They like that. They want that."

Amidst all the battles, McEnroe has developed something of a friendship with Connors. They practice together now, play Davis Cup together and seem to share a kinship in the wildness that rages within both of them.

McEnroe's friends, among them Davis Cup Captain Arthur Ashe, worry that people will remember McEnroe for his behavior, not his play. "Junior's too good for people not to talk about his tennis," said his doubles partner, Peter Fleming. "People can see his toughness in close matches. What they sometimes forget is he gets on himself as much as he gets on anyone else."

It is true that McEnroe calls himself as many names on the court as officials or fans. Imperfection is unacceptable to him, whether it comes from within or without.

And the surliness that is his trademark does not appear to be intentional. Consider the scene here Monday:

McEnroe, taking a break from a practice session with Fleming and Adriano Panatta, leaned against the grandstand, his Davis Cup jacket around his shoulders. A reporter approached and introduced himself. He asked a question.

McEnroe screwed his face into a pout. "Why do you have to ask questions the day before the tournament starts?" he asked. "That's ridiculous."

There was an uncomfortable silence. Then McEnroe again, voice still strident, but a tad softer.

"Look, anything I say now isn't going to interest anyone, anyway. It'll just be bull. When you get to this point, it's a matter of going out and playing, not talking."

Once again, Junior was right. Driven to confrontation, once again he managed to offend first and make sense later.