NEW YORK — When Melanie Oudin wakes up each morning these days, sharing a king-sized hotel bed with her mother, she's basically your average teen visiting the big city.

Then the 17-year-old from Marietta, Ga., gets out on court at the U.S. Open in those pink-and-yellow sneakers with the word "BELIEVE" stamped near the heel, and there is nothing ordinary at all about her.

No higher-ranked or more-accomplished opponent is too intimidating. No deficit is too daunting.

Yes, the comeback kid did it again yesterday.

Five points from a straight-set loss, Oudin kept plugging away with her perpetual-motion defense and pick-her-spots offense for a 1-6, 7-6 (2), 6-3 victory over 13th-seeded Nadia Petrova to reach the U.S. Open quarterfinals.

"It's kind of hard to explain how I've done it," Oudin said. "It's, like, now I know that I do belong here. This is what I want to do, and I can compete with these girls, no matter who I'm playing. I have a chance against anyone."

Can't argue with that. The upset of Petrova follows comebacks from a set down against three-time major champion Maria Sharapova in the third round, and No. 4 Elena Dementieva — a two-time Grand Slam finalist and Beijing Olympics gold medalist — in the second.

"I don't actually mean to lose the first set," explained a smiling Oudin, 17-4 this season in three-setters. "I sometimes just start off slowly, I guess. Maybe I'm a little nervous."

The first major quarterfinal of her nascent career will come against No. 9 Caroline Wozniacki of Denmark, who added to the stream of upsets in the women's tournament by knocking off two-time major champion Svetlana Kuznetsova, 2-6, 7-6 (5), 7-6 (3).

Asked about facing Oudin, Wozniacki said: "She's had an amazing run. Hopefully someone from the crowd will cheer for me."

Oudin is the story of the tournament so far, already drawing comparisons to Tracy Austin (a U.S. Open champion at 16) and Chris Evert (a semifinalist at 17), and giving U.S. tennis fans hope that there is someone coming up in the women's game behind the Williams sisters.

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

Things are different for the U.S. men: None of the 18 who entered the tournament is left, after 55th-ranked John Isner of Tampa, Fla., lost to No. 10 Fernando Verdasco, 4-6, 6-4, 6-4, 6-4. It's the first time in the history of an event that began in 1881 that there will be no American man in the quarterfinals.

"I knew that," Isner said. "I wanted to keep it going."

Verdasco, from Spain, will play fourth-seeded Novak Djokovic of Serbia in the quarterfinals, after Djokovic's 6-1, 6-3, 6-3 rout over 15th-seeded Radek Stepanek late Monday.

And Switzerland, of course, has its representative in the final eight: No. 1 Roger Federer extended his pursuit of a sixth consecutive U.S. Open title by beating No. 14 Tommy Robredo, 7-5, 6-2, 6-2. Up next is a familiar foe: No. 12 Robin Soderling of Sweden, who is 0-11 against Federer, including losses this year in the French Open final and Wimbledon's fourth round.

The woman who eliminated No. 1 Dinara Safina, Petra Kvitova of the Czech Republic, couldn't build on that, losing in three sets to Yanina Wickmayer of Belgium, while Kateryna Bondarenko of Ukraine shut out Gisela Dulko of Argentina, 6-0, 6-0.

This is all so new in so many ways for Oudin, who was ranked 221st and lost in the first round at the U.S. Open a year ago.

The situation seemed bleak yesterday when Petrova, already up a set, was serving at 4-3, 40-15 in the second. One more point, and Petrova would be a game from the win. But Petrova netted a forehand for 40-30, and on the next point, Oudin blocked back a 112 mph serve, then ended a 10-stroke exchange by smacking a forehand down the line.

"Unbelievable winner," said Petrova, who would never again be that close to victory.

"She's on a roll. And she has nothing to lose," Petrova said. "She's just having a blast out there."