US OPEN Venue: Flushing Meadows, New York Date: 31 August - 13 September BBC coverage: Live text commentaries on the website from 1600 BST each day, regular updates on 5 live, full commentary on 5 live sports extra in week two, both finals on 5 live
Safina holds the world number one ranking despite failing to win a Grand Slam title in her career to date
World number one Dinara Safina was knocked out of the US Open after an error-strewn display led to a 6-4 2-6 7-6 (7-5) defeat by Petra Kvitova.
Safina made 39 unforced errors and served nine double faults as the unseeded Kvitova, 19, won in two hours and 34 minutes.
Earlier, unseeded American Melanie Oudin beat former world number one Maria Sharapova 3-6 6-4 7-5.
But sixth seed Svetlana Kuznetsova won through, beating Shahar Peer 7-5 6-1.
It was the kind of result Kuznetsova's fellow Russian Safina was hoping for at the start of her match.
And although the 23-year-old will remain on top of the rankings regardless of who wins the women's title at Flushing Meadows, her loss to Kvitova added further fuel for those who argue that she does not deserve her number one status.
Safina was furious with the event organisers for shifting her match from Arthur Ashe Stadium to the smaller Louis Armstrong Stadium because of the late-running afternoon session.
"I'm the number one player in the world, why did they move me?" said Safina, whose game took place simultaneously with the other night match, Tommy Robredo's victory over James Blake.
"They just told us, 'We're switching you to Armstrong.' And basically that's it. It's very unfair."
Kvitova was guilty of 59 unforced errors, but she also fired 47 winners and only served five double faults.
It's a success in the sense that I'm back out playing tennis and hitting a tennis ball for a living - I'm lucky enough that I worked that hard to get back to being on the court
Safina is still seeking her first Grand Slam title, while Serena Williams, the second seed in New York, is an 11-time Slam winner and has alreadyb won Wimbledon and the Australian Open this year.
After losing the opening set, Safina came roaring back in the second, only to surrender an early break in the deciding set for the third match in a row.
She battled back for a 6-5 lead and forced three match points on Kvitova's serve in game 12 of the decider, but the Czech struck backhand and forehand winners either side of a mis-hit Safina backhand to see off the threat and hold.
In the tiebreak, Kvitova hit consecutive backhands long to put Safina 5-4 ahead, but the Russian then overhit a backhand to hand the Czech two match points.
Kvitova squandered the first with a forehand beyond the baseline, but when Safina sent the last ball long, it gave her the biggest victory of her career.
"I'm very happy," said Kvitova, who will play Yanina Wickmayer next. "It was amazing. Second set I was very down. I was not focused. It was terrible. Safina played very well.
"After that I concentrated on every ball and I won."
Oudin surprised Jelena Jankovic in the third round of this year's Wimbledon
Oudin, meanwhile, continued to add to a burgeoning reputation by disposing of Sharapova, having beaten Elena Dementieva in the previosu round and knocked Jelena Jankovic out of Wimbledon.
She will now take on Nadia Petrova, who beat Jie Zheng 6-4 6-1.
"I just kept fighting and fighting and tried as hard as I could," said 17-year-old Oudin. "I just can't believe it.
"She double-faulted a couple of times on important points and I kept putting pressure on her second serve.
"I served a really good last game and knew I needed to make some first serves, that was very important.
"I'm still realising I have beaten Maria Sharapova on Arthur Ashe Stadium in the third round of the US Open.
"I have played three Russians so far, Nadia Petrova is a good player but I think it will be a good match."
Sharapova made an incredible 63 unforced errors and 21 double faults but remained positive in defeat.
"With the amount of errors I made from both my groundstrokes and my serve, to be able to get it to three sets is not bad," said the 22-year-old Russian.
"If I didn't make those errors, those double-faults, I certainly would have won the match. So that gives me some confidence."
Three-time Grand Slam champion Sharapova spent more than nine months on the sidelines following shoulder surgery.
"It's a success in the sense that I'm back out playing tennis and hitting a tennis ball for a living," she said.
"I'm lucky enough that I worked that hard to get back to being on the court. I have to work not just as hard but harder to get back to the top."
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