Tropical Storm Dennis was the dominant player at the U.S. Open today, delaying and interrupting matches, thinning the crowds and making footing treacherous in at least one instance.

Mary Joe Fernandez, who spent six years ranked in the top 10, had dropped to No. 38 before this tournament, but she overwhelmed third-ranked Venus Williams in the first set on Arthur Ashe Stadium court this afternoon before succumbing. Williams showed signs of recovering by winning the first two games of the second set, and the match turned for good in the third game.

Fernandez, chasing a ball deep into the corner, slipped on a court glazed by drizzle and pulled her right quadriceps muscle. Fernandez, who had been initiating the attack, never returned to her first-set form and lost, 2-6, 6-1, 6-0, to a resilient Williams.

"It was definitely related to the rain," Fernandez said. "It started to sprinkle and the court gets very, very slippery right away. My foot just slid."

Play was suspended for about 90 minutes after Fernandez slipped, and she received treatment from a trainer. She returned with her upper right leg wrapped, but her movement was limited. She held serve to 3-1, but lost the next nine games as Williams picked up her own game.

The rain had interrupted the match earlier, with Fernandez leading the first set 5-1.

"It was kind of the same thing," Fernandez said. "I dragged my foot a little bit on the court, saw that it was kind of slick. I asked and we stopped. But once you get started, you want to keep playing. I thought maybe it's going to stop. But it was too slippery."

While Williams and Fernandez were able to complete their match, several others were hampered by rain and were postponed until Monday. The forecast in the New York area is for more rain on Monday, at times heavier than it was today.

Top-seeded woman Martina Hingis called it "a long day at the office, a lot of waiting" after her match was delayed from afternoon to evening. She waited through lunch, then dinner-"Pasta, but not a huge American portion"--before taking the stadium court. But Hingis wasn't complaining after her 7-5, 6-4 victory over 10th-seeded Arantxa Sanchez-Vicario.

Hingis said difficult losses at the French Open and Wimbledon this summer have been "an education" for her, adding that she has come to the final Grand Slam of the year, "Knowing what I want more."

It was Hingis's 12th straight victory over Sanchez-Vicario, who recorded 26 winners to 22 for Hingis. But Hingis committed only 17 unforced errors to Sanchez-Vicario's 29, and consistently won the pivotal points late in games.

"When she needed to, she played some unbelievable shots down the lines," Sanchez-Vicario said. "I played really well, but it's hard to beat the number one player in the world."

Also in the night session, ninth-seeded Greg Rusedski of Great Britan defeated American Chris Woodruff, 7-5, 3-6, 6-3, 6-4, to reach the fourth round.

American Todd Martin took a nap during the shower that delayed his match. When play resumed, Martin expected a tough match with Sweden's Magnus Larsson, who had won four of the six matches between the two. But acute tendinitis in Larsson's left knee forced him to retire after Martin had won the first set, 6-3.

It is the first time that Martin, the No. 7 seed, has advanced to the fourth round of the U.S. Open since 1995. It was a particularly disappointing loss for Larsson, who reached the quarterfinals here in 1997 and 1998.

"My knee has been feeling pretty bad the last few days," said Larsson, 29. "I've had a lot of bad breaks with injuries and health the last few years and I'm not getting any younger. If my body keeps treating me this bad--I don't know. I still love the game. I hope one day the injuries will be over and [I] can have a few good years."

Larsson was the latest player in the men's singles to retire from the year's final Grand Slam tournament with an injury. Top-seeded Pete Sampras and No. 11 Mark Philippoussis withdrew before playing a match. Defending champion Patrick Rafter and eighth-seeded Carlos Moya also retired with injuries.

Larsson said the tendinitis had prevented him from practicing the last couple of days, and it showed. Martin had done his own scouting and knew as much.

"I knew his knee was in some pain because one of my friends had told me that he was having trouble getting around the court on Friday," Martin said. "And right before the match, when he was getting his knee taped up, he had the trainer tape it right to the skin, which usually means he needs a little bit more support than usual."

Martin served eight aces, hit 23 winners (to Larsson's nine) and had little trouble winning the first set. "Maybe I could have played a few more games," the Swede said, "but no way I could finish the match."

While Larsson was betrayed by his body, 15th-seeded Amelie Mauresmo was betrayed by her game. The talented Frenchwoman missed 53 percent of her first serves, won only 58 percent of the points when she did land her first serve, committed 32 unforced errors and dropped a 6-4, 6-4 match to Germany's Anke Huber. In the second set, Mauresmo made good on just 38 percent of her first serves and hit three winners in the rain-interrupted match.

Huber, 25, joined the tour in 1990 and drew immediate comparisons to countrywoman Steffi Graf. But she has been in only one Grand Slam final (1996 Australian Open), never has reached the quarterfinals at the U.S. Open and came here ranked No. 27.

Huber had surgery on her right Achilles' tendon in April 1998 and didn't return until August. This year, she missed the French Open with a right foot injury. Mauresmo strained ligaments in her right ankle at the French Open in May, and played only two matches prior to the U.S. Open.

"This is a great success for me," Huber said. "It wasn't the best match, but I played smart."

Asked about the pressure of being compared to Graf, Huber said: "You get older, you see it in a different way. Sure it puts pressure on you if you're 16 and everybody is telling you, 'Second Steffi.' I won a couple of matches and she won I don't know how many Grand Slams."

CAPTION: Workers leave Arthur Ashe Stadium court during rain delay. Martina Hingis had match delayed until evening, when she beat Arantxa Sanchez-Vicario.