With just her second ace of the match, Nadia Petrova slammed home her arrival on the Grand Slam scene, joining two other Russian women -- Svetlana Kuznetsova and Elena Dementieva -- in the quarterfinals by upsetting defending U.S. Open champion Justine Henin-Hardenne, 6-3, 6-2.

But Henin-Hardenne -- who will cede her No. 1 ranking to either Amelie Mauresmo or Lindsay Davenport with the loss -- wasn't the only former Open victor dropped from the tournament on Monday, as two-time champ Venus Williams got swept out in straight sets by the streaking Davenport.

In their late afternoon match, it seemed as if Davenport and Williams were simply willing the last game to go on. With nine deuces, five break points and five match points in that game, the players seemed to make the impossible shot -- or miss a key stroke just over the line -- over and over again.

Finally, with a flailing forehand sent long, Williams bowed out of the Open as a look of sheer relief crossed Davenport's face. The 7-5, 6-4 victory sent Davenport to a quarterfinal matchup with the last unseeded player left in the women's draw, 62nd-ranked Shinobu Asagoe. Asagoe took out No. 29 Eleni Daniilidou, 7-6, 4-6, 6-3.

In the other fourth-round action, No. 9 Kuznetsova erased Mary Pierce, setting up a showdown with Petrova.

"It was such a tough game," Davenport said of the last one against Williams. "You know, it probably should have been 5-all. I didn't play the greatest game. But, still, to come out and win it, pretty exciting. She came up with a few good shots."

Davenport won the match with her serve, but Williams also lost it with her forehand. Most of her 42 unforced errors came off a forehand that wasn't controlled or consistent.

"I'm not necessarily going for winners, but I'm going for an aggressive shot and to make a play," Williams said. "I'm not very comfortable just, like, sitting back and hoping the next person will miss. Ultimately that's not how you win. Ultimately the people who are winners are the ones that make it happen."

While Williams didn't help her cause with her forehand, Davenport was never in any danger on her service games -- until the final one. In extending her winning streak to 21 matches, she faced her first break point in that game. Davenport had been down on her serve only once in the match, at 0-15 in the fourth game of the second set.

"I came up with some good serves and good forehand winners to set it up," she said of the final game. "But then, you know, wrongly so, I was then waiting for her to make the error. You know, you probably shouldn't play like that, but she was giving me so many errors, it's hard to then go for shots and miss them."

The match was one in a series of battles between the two. Davenport broke a tie by winning the 25th contest between them, going up 13 to 12.

With four straight singles titles under her belt, Davenport came into the Open on quite a roll, and now has taken out her four opponents in straight sets.

Williams, who continued to struggle with her serve, has been on the opposite tack, working through wrist and ankle injuries that have plagued her throughout the summer.

If Davenport makes it past Asagoe, the rest of her draw may have gotten easier with the ouster of Henin-Hardenne. The American would face the winner of the quarterfinal match between Petrova and Kuznetsova.

The 22-year-old Petrova beat the No. 1 seed without a lot of trouble, winning in less than an hour and a half. Henin-Hardenne's loss marks the earliest an Open No. 1 seed has lost since Billie Jean King was defeated in the third round in 1973.

"Today I was more mentally strong," Petrova said. "I kept my nerves down. I really focused on every point. I tried to give her as many balls as possible and also come to the net, put kind of a pressure on her. I really was holding my serve well."

Henin-Hardenne contributed 30 unforced errors to the 70 points won by Petrova. She had just three forehand and three backhand winners in the two sets.

"It's not easy," Henin-Hardenne said. "I miss this kind of tournament, that's for sure. Now that I'm healthy and I can play, I'll need matches, I'll need tournaments and I'll need till the end of this year to be ready."

Henin-Hardenne, who missed four months of tennis while suffering from a viral illness, had just a single break point opportunity in the match when Petrova slipped a bit in her final service game. Serving for the match, Petrova sent a forehand into the net, but quickly recovered on an error by her opponent and the ace.

"It wasn't my day," Henin-Hardenne said. "I wasn't in confidence and when you're not in confidence, you don't feel any security in your game."

As for Petrova's next opponent, Pierce couldn't come up with another upset of a top 10 Russian player, falling to Kuznetsova after taking No. 7 Maria Sharapova out of the tournament in the third round.

Kuznetsova had her serve working in the 7-6 (7-5), 6-2 victory over Pierce, slamming 13 aces and winning 83 percent of her first serve points.

It took the full three sets, but Asagoe kept her upsets coming with the victory over Daniilidou. Asagoe has taken out three seeded players so far, but isn't happy with just making the quarterfinals. She has her sights set on something no one has been able to do recently -- beat Davenport.

"I was trying my best to just keep going, but still I probably can go further," she said through an interpreter. "So I'm not really satisfied right now. I have to go further from here."

Justine Henin-Hardenne suffers earlierst loss for a women's No. 1 seed in the U.S. Open since 1973. Lindsay Davenport stops Venus Williams, 7-5, 6-4; next up is unseeded Shinobu Asagoe.