Gritting her way through a shaky third set, the 70th-ranked player from Marietta, Ga., pulled off her second upset of the Open on Saturday, defeating a more-seasoned, more-famous, more-moneyed opponent - 29th-seeded Maria Sharapova, 3-6, 6-4, 7-5.
"I don't even know what to say right now," Oudin said, choking back tears in her postmatch interview in Arthur Ashe Stadium. "Thank you so much for cheering for me."
Sharapova, who has won this tournament once, usually gets those cheers. But on this cloudless day in Queens, the fans were rooting for a new potential queen - the one who stamped the word "Believe" on her shoes, but probably didn't see this coming so soon.
"My goal was to make the top 50," she said. "But if I keep playing like this, who knows? Hopefully, I can get as high as anything."
She added this upset to one over No. 4 Elena Dementieva in the second round and a win over former No. 1 Jelena Jankovic earlier this year at Wimbledon.
Her confidence is growing as quickly as her resume, and suddenly, it does seem like anything is possible.
Her fourth-round match is against No. 13 Nadia Petrova of Russia, though there's a sense she may have already knocked out the two toughest players on her side of the draw in Dementieva and Sharapova. No. 5 Jankovic is also gone, along with No. 11 Ana Ivanovic. No. 1 Dinara Safina is still there, but she has been playing poorly so far.
The Williams sisters are on the other side of the draw and it may not be too early to dream about the third-best American, Oudin, going against one of the two best for the U.S. title.
"I've always been so competitive," Oudin said. "I go out there and fight as hard as I can. I have 'Believe' on my shoes. That's what I did today. I ended up winning and I'm just so happy."
In men's play, No. 1 Roger Federer extended his winning streak to 37 at the U.S. Open, overcoming some shaky play throughout for a 4-6, 6-3, 7-5, 6-4 victory over No. 31 Lleyton Hewitt.
It was Federer's 14th straight victory over Hewitt, a former No. 1 who won the U.S. Open in 2001.
"I just had to believe that I could still turn this around," Federer said. "And with the great streak I have against him, I knew that if I could get back into the match then I could get back on a roll, because I've done it so many times against him."
Oudin and Sharapova followed Federer onto the show court but Sharapova did not put on a headliner's performance.
She served 21 double-faults - the equivalent of five-plus games - committed 63 unforced errors and clearly hasn't rounded fully into form after nearly 10 months off with a shoulder injury that forced her to miss the trip to Flushing Meadows last year.
Sharapova and Oudin traded three breaks each through the first four games of the third set, then Oudin got a fourth break to go ahead 5-4. She responded by holding serve, closing the match with a crosscourt winner off a short counterpunch from Sharapova.
Oudin dropped her racket and choked back tears, shook hands with Sharapova and walked to her chair, shaking, clearly having trouble believing what had taken place.
But, yes, that happened.
"I just kept fighting as hard as I could, tried as hard as I could," she said. "I just can't even believe it."