The result was a foregone conclusion, the match a necessity rather than a challenge.

But there came a point at 4-0 in the second set of Martina Navratilova's opening-round match at the U.S. Open today when the technical skills and physical prowess that have made her the No. 1 women's player in the world could be seen in the vivid isolation of one seemingly implausible backhand.

Navratilova had been attacking all day, forcing the action, forcing Emilse Raponi Longo into inevitable errors. At 15-15, Raponi Longo looked up from her serve and saw Navratilova at the net. She decided to lob.

Navratilova gazed briefly over her shoulder, glided to the base line, pirouetted into position and hit a backhand passing shot down the line.

She smiled at her coach, Mike Estep, sitting at courtside, and pointed, as if to say, "One for you." They had talked about the shot Wednesday in practice, about the right time to use it. Her decision in that instant of execution, her ability to get to a ball others would not have reached, and then do something with it, explain why her match record is 60-1 this year, 150-4 in the last 18 months. It explains why Raponi Longo was able to win only 25 of 79 points, only eight off Navratilova's serve (two on double faults) and lost, 6-1, 6-0.

In politics, there is the gender gap. In tennis, there is the Navratilova gap, and the gap between Navratilova and the rest of the women on the tour seems to be getting wider all the time. Estep replaced Renee Richards as Navratilova's coach at Eastbourne, just before Wimbledon. Navratilova says Richards made her game sound and "Mike has expanded it."

Her game is an extension of her personality. "I'm not very patient," she said. "I'm not one to wait for others to make mistakes. I want things to happen. If I'm going to take a photograph of a flower, I'm not going to wait for it to open. I'm probably going to bring the sun over to it."

Forcing things is the essence of Navratilova. She says the ball no longer dictates to her, she dictates to it and her opponents along with it. "She's making the first move," Estep said. "She is white on the chessboard and makes everyone else black."

Not that long ago, she was bragging about her ability to stay back and rally with the base liners if she needed or wanted to, so improved were her ground strokes. For others, that is the safest strategy; the percentages are with them at the base line. But the percentages are with Navratilova when she is at the net.

"She views herself as a gambler, which in fact she isn't," Estep said. "She's being aggressive. But she's not gambling. Gambling is when you play against the odds."

The odds are not great that anyone will be able to pass her 50 times a match. Estep says there were only six or seven balls today on which she could have come in but didn't.

Arthur Ashe said, "She's like the old Green Bay Packers. You know exactly what she's going to do but there isn't a damn thing you can do about it."

There are many reasons why. As a lefty, she has a natural advantage over many of her opponents. Her forehand cross court plays into a right-handed opponent's weaker backhand, while Navratilova covers the shot down the line. "She wins oodles of points that way," Ashe said.

Her serve is also an advantage. Now, in addition to the slice serve to the ad court, which she uses 60 percent of the time, and the flat serve she uses 25 percent of the time, she has a kick serve that twists away from the receiver in the deuce court. "She has the ability to pull the opponent wide out on either side of the court," Estep said.

Estep began with the premise that she has the best volley in the women's game and decided to improve it. He wants her to cut down on her swing but strengthen her forearm so she can hit as hard.

The shorter the swing, the better the timing and the less likely she is to make errant volleys, on which she made most of her errors in the past. Estep also has coached her not to hit an overhead from the backhand side, which leaves her vulnerable, but to backpedal and hit it as a forehand.

Navratilova's greatest strength is her athleticism and her athleticism is enhanced by her strength. She says basketball has made her quicker, improved her footwork. "She scrambles so well," said Pam Shriver, her doubles partner.

Estep says she takes virtually every forehand on the rise, which cuts down the amount of time her opponent has between shots. "She takes the ball so quickly, if it doesn't bounce predictably she's at a disadvantage," said Ted Tinling, director of player liaison on the tour and a historian of the women's game. "That's why I think Chris (Evert Lloyd) can only beat her on a bad court now."

Tinling says Navratilova's performance this spring at the Virginia Slims of New York was the best women's tennis he has seen since Suzanne Lenglen. Others are not quite ready to canonize her. Ashe said, "She's still not as good as Billie Jean (King) or Margaret Court. Her record is not yet as good as Chrissie's."

It is possible to be too gifted. The challenge of making the impossible shot can entice you away from making the right one. "She has too much flair," Estep said. "She has to cut it down. I'm careful in practice when she tries a fancy shot (not to discourage her). She's so talented, it would be unfair for the world not to be able to see them."

Instead, he cautions her to use them at the right time--at 4-0, say, in the opening round of the U.S. Open, the tournament she has never won. "I guess that makes me the underdog," she said.

It is unclear how much better she can get with Estep providing the most physical challenges on the practice court. Tinling says she must derive the challenge from the pride of performance, as Lenglen did. He tells the story about the time when Al Laney, the sportswriter, told Lenglen, "You missed two returns of serve this week. She said, 'Yes, one on Wednesday and one Friday. Wasn't I careless?' "

Estep said, "I think she wants to be become the greatest player who ever lived. I hope for her sake that there is a challenger to her throne. Every great athlete always had someone to push him."

The day was nice for John Lloyd, husband of Chris Evert Lloyd, who upset 10th-seeded Jose Higueras, 6-3, 6-4, 7-5. And it was easy for Jimmy Connors, the defending men's champion, who beat Thomas Hogstedt, 6-1, 6-2, 6-3. But it was anything but nice and easy for sixth-seeded Guillermo Vilas, who barely survived a traumatic five-set match with 124th-ranked Tom Cain of Richmond, 6-7 (5-7), 6-3, 6-3, 2-6, 6-2.

Cain, who had trailed, 4-1, in the first-set tie breaker, refused to give up. In the first game of the fifth set, Vilas had to save four break points.

But with Vilas serving at 1-1, deuce in the fifth set, Cain sent up a weak lob, stumbled and collapsed by the scoreboard at the north end of the stadium. His chronically weak left ankle had gone out.

As Cain lay on the ground in pain, Vilas put away an overhead, then went over to see how he was. At first, Cain said, he wasn't thinking about continuing, "just surviving." Then, as Cain's ankle was being taped, umpire Stephen Winyard called him for delay of game (having exceeded the three-minute limit). He got up in time for Vilas to serve out the game. Cain persevered, but is movements were tentative and Vilas broke to go ahead, 3-1.

"It was a completely different match after that," Vilas said. "I was in there," Cain said, when asked how he thought he would have done if not for the fall. "I was playing well, and he was getting tentative and the New York fans were going berserk."

He got a standing ovation as he left the court.