And on the fourth day, there was sunshine.

For almost the entire afternoon, the sun hovered over the All England Club, interrupted only briefly by rain. Before dusk finally stopped play, there had been only one loss by a seeded player but the day still was filled with remarkable moments.

Consider that all this happened in seven hours:

Hu Na, the Chinese defector who has lived in California since 1982, upset English model-tennis player Annabel Croft, 6-3, 7-5, in Hu's first match at Wimbledon.

Chris Evert Lloyd, showing no signs of the stiff neck that bothered her last week, won her first match from Mary Lou Piatek, 6-1, 6-0, in a 40-minute wipeout. "The neck," Evert said, "is fine, 100 percent okay."

Tom Gullikson, the left-handed Gullikson twin, pulled the one major upset of the day, beating 12th-seeded Miloslav Mecir in a match that had the crowd at Court 1 gasping throughout as it twisted and turned.

Boris Becker, the 17-year-old West German who might be the game's next superstar, finished his match against Hank Pfister, winning, 4-6, 6-3, 6-2, 6-4. Afterward, Pfister said simply, "Of the 128 players in the draw I can think of about 124 I would rather have played. He's that good already."

The one true upset of the day was the victory by Gullikson who, at 33, thinks this might be his last Wimbledon because his daughter starts school this fall and he isn't sure he wants to continue to travel without his family. Gullikson upset Mecir, 4-6, 6-3, 6-4, 6-7 (5-7), 6-3, in a match filled with superb shot making and warm feelings between the two players.

The final point of the match said it all. Mecir had come back from a 5-1 deficit to trail, 5-3, 40-30. Gullikson came in behind a forehand and Mecir hit a two-fisted backhand cross court for what looked like a sure winner. Gullikson twisted to the right and, falling, backhanded a volley.

The ball just skidded across the net. Mecir had no chance to get to it as Gullikson lay on the ground, having jammed his thumb as he fell. Except that Mecir, somehow got to the ball, lunging at it head first. He got his racket on the ball and pushed it over Gullikson's head. But the ball landed an inch beyond the base line.

Both players lay on the ground for a moment, stunned. Then they got up and just looked at each other as if to say, "How'd you do that?" Finally, Gullikson, realizing he had won, walked to net, put his arm around Mecir and looked to the heavens in thanks.

"I sure didn't want to play another point," he said. "I couldn't believe he got to that ball. When I was lying on the ground I was just praying the ball would be out."

It was, and Gullikson, who is ranked No. 99 in the world, had one of his most gratifying victories. Other seeds escaped Mecir's fate, but in some cases, narrowly. Most notably, sixth-seeded Pat Cash, a semifinalist here a year ago, had to go five sets before beating Todd Nelson, 2-6, 6-2, 7-5, 6-7 (6-8), 6-3.

Among the women, Hana Mandlikova (No. 3), Manuela Maleeva (No. 4) Helena Sukova (No. 7), Wendy Turnbull (No. 14) and Kathy Rinaldi (No. 16) joined Evert as straight-set winners. Only Shriver (No. 5), Steffi Graf (No. 11) and Carling Bassett (No. 13) had any trouble.

Shriver had split sets with Anne White when the match was called because of darknees. Graf and Bassett each dropped a set, then went on to win, Graf beating Lisa Spain-Short, 6-7 (5-7), 6-4, 6-2. Spain is best known for being sponsored by country singer Kenny Rogers. She finally wore down against Graf, who at 16 is the player most often mentioned as likely to challenge Gabriela Sabatini as the heir to the Evert-Martina Navratilova throne.

Other than Cash and Mecir, the only seeded men to play were Tomas Smid and Kevin Curren, who each won easily in straight sets. Henrik Sundstrom, the highest-ranked nonseed in the field, wasn't as lucky. He lost to Greg Holmes, the former NCAA champion who hits all his ground strokes two-fisted, 6-3, 4-6, 6-7 (3-7), 6-4, 6-2.

Early in the day, Virginia Wade, the beloved "Our Ginny" of the British, began her 24th and final Wimbledon with a 6-4, 7-5 victory over Leah Antonoplis. Playing on jam-packed Court No. 2, Wade, who is 39, looked as graceful as she did when she won the championship in 1977, hitting her ground strokes firmly and pinning Antonoplis on the base line throughout the match.

"I'd really like to get far enough to play one of the top-notch players," Wade said. "I'd like to go out there with a bit more devil-may-care because the mind is the thing that inhibits good tennis. This is an opportunity for me to play without pressure."

If Wade wins another round, she might play Shriver, a match that would certainly be on Centre Court, giving her a genuine chance for one last glorious day on these courts where she has now played 197 matches.

That is exactly 196 more than Hu. Since her defection in July 1982 during a Federation Cup match in Santa Clara, Hu has had little success in tennis. She is ranked 150th on the computer, has played mostly satellite tournaments and had earned $2,075 this year.

But she won three qualifying matches to get into the Wimbledon draw and today served and volleyed superbly to upset the glamorous Croft, one of the English fans' darlings because of her dazzling looks. After today, Croft, who is 19, might concentrate more on her burgeoning modeling career.

Hu will continue to play tennis. "I think I have improved very much," Hu said. "For a while, every time I started to play better, I got hurt and had to stop. Today, just to play here was a dream come true whether I won the match or not."

Since her defection, Hu, who is 22, has not spoken to her parents, able to communicate by letter only. Tonight, she went back to her hotel to write a long one.