Melanie Oudin extended her remarkable run at the US Open to the quarter-finals with another come-from-behind victory, 1-6, 7-6 (2), 6-3 over 13th-seeded Nadia Petrova.

The 17-year-old Oudin staved off two points that would have put her behind 5-3 in the second set, then rolled through the third, hitting corners with those underrated groundstrokes and taking advantage of 22 unforced errors by her more-seasoned, higher-ranked opponent.

Rankings, like her age, however, are only numbers.

The 70th-ranked player already had wins over No. 4 Elena Dementieva and No. 29 Maria Sharapova at Flushing Meadows, along with one over former No. 1 Jelena Jankovic this summer at Wimbledon. Now, she's knocked off No. 13.

She has become the youngest American to move into the quarter-finals at America's Grand Slam since Serena Williams in 1999.

"I think this is going to do a lot," Oudin said. "I think it's good for American tennis."

Not so good for Russian tennis, though. All four of Oudin's wins have come against Russians and her next match could be against yet another. That's sixth-seeded Svetlana Kuznetsova, the 2004 Open champion and the only Grand Slam tournament winner left on Oudin's side of the bracket.

Career Grand Slam

"It's kind of hard to explain how I've done it," Melanie said. "Today, there were no tears because I believed I can do it. Now I know I do belong here. This is what I want to do. I can compete with these girls no matter who I'm playing. I have a chance against anyone."

In men's action, No. 1 Roger Federer beat No. 14 Tommy Robredo 7-5, 6-2, 6-2 for his 38th straight win at the US Open. In the quarter-finals, Federer will face No. 12 Robin Soderling, who he beat in the French Open final to complete his career Grand Slam. Soderling advanced when No. 8 Nikolay Davydenko retired with a leg injury at the start of the fourth set.

In other women's matches Monday, Kateryna Bondarenko and Yanina Wickmayer won to set up a quarter-final between two players ranked in the 50s. OK, who had that one filled in on their brackets?

Meanwhile, Oudin is electrifying the other side.

Four of the top five seeds are gone, with only No. 2 Serena Williams bringing any sense of stability to the proceedings. She has yet to be challenged in any of her four matches.

Could Oudin eventually be the answer?

"Right now, I think she'll play Serena in the finals," said Oudin's twin, who left New York after the first round but flew back for this one.

"We're not going anywhere," she said.