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 US 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 on Monday.

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 US 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 US Open champion at 16) and Chris Evert (a semifinalist at 17), and giving US 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."

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.

Like Oudin and Wozniacki, Wickmayer and Bondarenko are first-time Grand Slam quarterfinalists.

This is all so new in so many ways for Oudin, whose twin sister, Katherine, was bawling in the stands at match's end.

A year ago, Oudin - it's pronounced "oo-DAN" - was ranked 221st and lost in the first round at the US Open. She never had won a Grand Slam match until June, when she knocked off former No 1 Jelena Jankovic en route to Wimbledon's fourth round - after losing the first set, naturally.

My, how her life is about to change. Starting to change already, actually.

After beating Petrova, Oudin huddled with her coach, Brian de Villiers, trying to figure out how to squeeze in various media obligations with necessary tasks such as eating something and getting treatment for her heavily wrapped left thigh.

Endorsement offers are coming in. Now recognized by strangers, Oudin needs security guards to help her navigate the crowds on her way to the Open's practice courts. Walking through the lobby of her New York hotel is an adventure. There even was a bit of a skirmish among paparazzi when she was in Times Square the other day.

"That was her first realization that she's big-time, that it is going to be scary sometimes," Katherine said. "I'm surprised that she's held it together as well as she has."

On the court, the situation seemed bleak 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 an 10-stroke exchange by smacking a forehand down the line.

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

"Winning that game kind of gave her a second breath," Petrova said. "She realized, 'OK, I'm back in the game'. And probably after winning previous matches pretty much in the same way, she thought, 'You know, I can do it again'."

Precisely right.

Forced to hit extra shots because of the 5-foot-6 Oudin's ability to track down balls and sling them back, Petrova began to make more and more mistakes. During one key stretch early in the third set, Oudin won 11 of 13 points - and 10 were thanks to miscues by Petrova.

"She's on a roll. And she has nothing to lose," said Petrova, the fourth Russian in a row Oudin has beaten. "She goes, enjoys it, crowd is behind her. She's just having a blast out there."

Sure is.

"This," Oudin said, "is what I've wanted forever."

Not that forever is all that long in her case. She is, after all, "just 17" - as the lyrics go in the Beatles song reverberating through the Arthur Ashe Stadium sound system after her victories there.

Melanie and Katherine began hitting tennis balls out of a bucket with their grandmother at age 7, then began working with de Villiers at age 9. At about 12, though, Melanie decided she wanted to be home-schooled, so she could focus squarely on tennis. Katherine, meanwhile, plays in national junior tournaments, but has other interests, and is now a senior in high school.

As little kids, the sisters would play matches on a makeshift court, piling up jackets in their home's cul de sac to serve as a net until Mom or Dad said it was too dark to be outside.

They never pretended, though, that they were at Flushing Meadows or the All England Club. Those places seemed too far away at the time.

"It's not like we were saying, 'Oh, we're going to be there one day'," Katherine said. "But Melanie's just always believed in herself. It's amazing."

(AP via China Daily September 9, 2009)