When it was over, Pam Shriver said she was sorry. As they walked off the court, she put her arm around Martina Navratilova, her doubles partner, her friend, and apologized for beating her in the quarterfinals of the U.S. Open. Only the net and Shriver's victory came between them.

Shriver, the No. 7 seed, had ended Navratilova's quest for the Grand Slam, and for the only major title she has not won. She had beaten Navratilova, the No. 1 seed, the No. 1 women's player in the world, 1-6, 7-6 (7-5), 6-2. She had driven Navratilova out of the tournament she wants to win most, just as she did in 1978.

"I said I was sorry," Shriver said. "I don't know why."

Shriver said she played "the best match of my life." Navratilova wanted to and didn't. Last year, Navratilova lost in the final to Tracy Austin and cried when the crowd cheered. Since then, she has won a total of 68 matches, including the Australian Open, Wimbledon and the French Open.

Today, her reddened eyes offered a jarring contrast to the unequivocal confidence she displayed all week. "It's not bitter," she said of the loss, only her second of the year, that ended a 41-match winning streak. "It's the most disappointing. In one way, I'm glad it was Pam and nobody else. I wish she could be more happy than she was."

If there was any bitterness, it was at the thought that she would spend another year known as someone who becomes unnerved by the Open. "I don't want that label put on me," she said. "And I don't deserve it."

So, although she ran the risk of sounding "like sour grapes," she revealed she has had an acute case of toxoplasmosis, a disease that weakens the muscles. "My strength was just seeping from me in the second set," she said. "In the third set, I just couldn't run."

Navratilova said she contracted the disease during the Federation Cup in July after eating a bowl of nuts that had been contaminated by cat hair.

Later tonight, Navratilova said she had not talked before about the ailment because "it was a crutch and I didn't want to use it."

She also said she would continue to play doubles with Shriver in the tournament.

Dr. Gary Wadler, a tournament physician, had performed blood tests this week confirming the diagnosis. "I told her to moderate her practices, rest as much as she could and try to win, 6-1, 6-1," he said.

Shriver, who had mononucleosis earlier this year, said, "Any time you win the first set in 17 minutes and are serving for the match at 5-4, 30-15, you should win the match no matter what disease you have . . . I'm not mad at Martina. If it's true, it may have affected her. I tend to believe it didn't because I know how I played."

After several almost languid days, Shriver, of Lutherville, Md., and Rodney Harmon, who is from Richmond, Va., made the Open come alive. Harmon, a wild card, beat eighth-seeded Eliot Teltscher, 6-4, 4-6, 6-3, 3-6, 7-6 (7-1).

Harmon plays for Southern Methodist University, but he learned how to play tennis in Rock Creek Park in Washington, where his teacher was Willis Thomas.

He learned well. Although he double-faulted twice serving for the match at 5-3 in the fifth set, once on match point, he won all but the first point of the tie breaker, the last point one of 13 aces.

Also advancing were five-time champion Chris Evert Lloyd, who defeated No. 16 Zina Garrison, 6-4, 6-3, and Tom Gullikson, who beat Jaime Fillol, 6-4, 6-3, 6-3.

Defending champion Tracy Austin, seeded third, was leading No. 5 Hana Mandlikova, 5-4, in the first set when rain stopped the match. It will be concluded Wednesday.

Guillermo Vilas, No. 4, was behind two sets to 12th-seeded Steve Denton, who had 25 aces, and came back to win the last three, breaking in the eighth game of the fifth set.

Ilie Nastase's old antics were there and so were some of the shots, but they weren't enough to beat Jimmy Connors, who won 6-3, 6-3, 6-4. At break point in the second game, umpire Frank Wilie called Nastase for a penalty point, giving Connors the game and a 2-0 lead.

Connors walked to the other side of the court and told Nastase, "Let's cool it. This guy's after us. Let's just play tennis."

Nastase, who later threw a towel at Wilie and cursed him, was fined $1,000. Connors, saying the officiating got in the way of the tennis, pleaded: "Let the players go." He plays Harmon in the next round.

But the day belonged to Shriver. It has been a long time coming, since she lost in the final here to Evert in 1978.

She appeared distracted in the first set, and lost it quickly. In the second set, Navratilova saved two break points in the second game, and then broke in the ninth. But Shriver broke back. They went to a tie breaker. Shriver double-faulted to make it 2-all, but won the next two points. Shriver netted a backhand to make it 4-3.

Shriver remembered her feeling. A second service ace made it 5-3 and high backhand cross-court volley made it 6-3. Perhaps Navratilova had forgotten just how long Shriver's arms are, how she virtually can reach across the Long Island Expressway to pick off a volley. "She keeps stretching that arm, it's like an antenna," Navratilova said.

Navratilova won the next two points on her serve, but Shriver, serving on her third set point, ever so gently lifted a backhand cross-court volley over the net that went dead at Navratilova's feet.

Navratilova grew weaker; Shriver gained strength and conviction. Leading, 5-2, in the third set, she went to the side, buried her head in a towel and came out to serve for the match. Navratilova had a lot to lose, but she didn't care about the money (she had already won $500,000 in the Playtex Challenge Series for winning three other tournaments; winning the Open would have meant another $500,000).

A return winner by Navratilova gave her break point 30-40, but a wide backhand pulled them even. Another faulty backhand betrayed her.

It was match point for Shriver, year point for Navratilova. Shriver missed her first serve. Twice Navratilova tried to pass wide to Shriver's forehand and Shriver volleyed back, the second a mis-hit that looked like a drop shot. Navratilova charged and scooped the ball across the net.

Shriver summoned all her potential, her years of frustrations from a chronically sore shoulder, and gathered it into the final shot: a backhand volley that almost hit Navratilova.

"I just zoned," Shriver said. "I think that's the word. I don't use it very much." No apology was necessary.