Perhaps the reason they don't get along is that whenever Bill Scanlon glares across the net at John McEnroe, he sees what could have been.

Scanlon is 26 and is still best known for being the 1976 NCAA champion. Nobody remembers McEnroe for being the 1978 NCAA champion. "He's got a chip on his shoulder about certain things and I've got a chip on my shoulder about certain things," McEnroe said.

"Some feel Bill has never climbed higher in the world rankings because his mind is subject to distraction," says the Grand Prix media quide, damning him with faint praise. "He is a talented guitarist and a few years back at the Maui tournament he struck up a fast friendship with jazz guitarist George Benson."

Scanlon, who was the champion of Maui in 1978-79, said, "If I could rip the pages out of the media guide, I'd like to. All they ever write about is what happened in 1978. All they think is that I go play guitars on the beach. This is something we've been working on, trying to ditch, for about three years now, trying to show that I'm back doing what I'm supposed to be doing.

"I made a promise to myself about three years ago that I would never, ever give up on a match, and would devote myself to any match as if it was this match today at the U.S. Open."

Appropriately, he beat McEnroe in the 1978 Maui tournament as a "lucky loser,' after first considering taking a sabbatical from tennis. He was a quarterfinalist at Wimbledon in 1979, beat Bjorn Borg in 1980 and last beat McEnroe in 1981 in San Francisco. Why the change in attitude? "I just realized what an opportunity I had," he said. "This was after about four years on the pro tour . . . Finally, somehow I realized what I was squandering. It made me sit back and realize: 'Is this the way I really want to finish out?' "

In February, he began working out informally with Warren Jacques, who coaches Kevin Curren (who beat Jimmy Connors at Wimbledon) and Steve Denton. "We've been working on his head and we've been working on his mind," said Jacques, whose proteges have beaten the No. 1 seeds at Wimbledon and the Open.

"Bill has an image to shake off among his fellow pros," Jacques said. "He had a tendency to complain, to winge--that's an Australian word--a little too much. He's not letting little things bother him."

Scanlon, a fast-court player, said Jacques had been yelling at him to "get in, hit hard, force him."

Force McEnroe he did. Especially in the big points, something he has been working on, playing 50 tie breakers in practice this summer. At Wimbledon, he realized his loss to McEnroe came down to five or six big points in the tie breakers.

"He's got a little bit of a security problem," McEnroe said. "There's no reason he should because he's a real good player. Something like this will help him get over the hump because he doesn't need to be the way he is."

Scanlon says he is very attentive when he plays McEnroe, very determined. You could see it in his face as he waited for McEnroe's second serve on his second match point, stepping into his backhand return and hitting it down the line. "When I saw my shot go in, when I saw it go past him, I had no control of my reaction," he said.

His fists were in the air and the cry was a yelp of delayed gratification.