Venue: Flushing Meadows, New York Date: 31 August - 13 September
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Fourth seed Dementieva and fifth seed Jankovic went out in quick succession
Elena Dementieva and Jelena Jankovic became the first big-name casualties at the US Open with second-round defeats.
Fourth seed Dementieva lost 5-7 6-4 6-3 to American teenager Melanie Oudin, who survived a thigh injury in the third set to close out a famous victory.
Fifth seed Jankovic, the runner-up last year, lost a thrilling encounter against Yaroslava Shvedova of Kazakhstan 6-3 6-7 (4-7) 7-6 (8-6).
Dinara Safina laboured to victory but Maria Sharapova powered through.
World number one Safina defeated Germany's Kristina Barrois in three sets, while 2006 champion Sharapova, seeded 29, beat Christina McHale 6-2 6-1 in the night session to set up a match against Oudin in the third round.
"I thought she played great tennis," Sharapova said of her next opponent.
"To beat someone who's been playing great all year long, and number four in the world, it's a darn good win.
"I expect to go out there and for her to play some of her best tennis."
Oudin said after her win: "I don't even know what to say right now. I'm so excited. You have no idea."
I was very sad and emotionally I was really not on court
Jelena Jankovic on the death of her grandmother
The 17-year-old defeated Jankovic in the third round of Wimbledon and showed great tenacity to beat another leading name on Arthur Ashe Stadium.
In a match that had 13 breaks of serve, Oudin led 2-0 in the third set but Olympic champion Dementieva edged a lengthy third game.
Oudin took a medical timeout for treatment on an injury to her left thigh and, despite returning with her leg heavily strapped, broke her opponent to lead 3-1.
The American, clearly in pain and struggling to hold back the tears, then dropped her serve but went on to win the next three games.
Dementieva took the next game to trail 5-3 and saved two match points before failing to clear the net from an Oudin first serve.
"Going into that last point I was thinking I might not get another chance so I just had to go for it with a big serve and I was lucky it went in," added Oudin.
"The crowd supporting me helped me get through."
Dementieva admitted: "She was in the court, not afraid to play, playing very aggressively, really enjoying this atmosphere and the crowd support. It looks like she has a good future."
An epic contest followed between Shvedova, ranked 55th in the world, and Jankovic that lasted two hours and 40 minutes.
Shvedova, 21, won the match with an ace to cap off a gutsy performance during the final set tie-break
Jankovic, who blew hot and cold during the contest, had two match points but her opponent won four successive points after trailing 4-6.
And the Serb later revealed that she had struggled to be focused after her grandmother died on Wednesday.
"I was very sad and emotionally I was really not on court," said Jankovic. "I really tried my best to be there and to try to play, but it was really hard."
Shvedova's reward for defeating Jankovic is a third-round meeting with Argentina's Gisela Dulko.
Dementieva and Jankovic may have succumbed to shock exits but there were no such problems for sixth seed Svetlana Kuznetsova.
The Russian defeated Latvia's Anastasija Sevastova 6-4 6-2 and will meet the winner of the contest between Shahar Peer in the third round.
Safina survived a huge scare to beat Australian world number 167 Olivia Rogowska in her first-round match - and she again looked out of sorts against Barrois, particularly with her brittle serve.
The Russian, who has never won a Grand Slam, made 15 double faults during a match that lasted more than two hours but eventually won 6-7 (5-7) 6-2 6-3.
Barrois looked set to pull off a real upset when she took a 2-0 lead in the third set but Safina showed great determination to win four of the next five games.
The German then had four break points to level at 4-4 but Safina held her nerve to move two games clear and broke Barrois to take the match.
"Another tough day at the office," said Safina afterwards.
"I don't want to play three sets. Don't think I want to lose the first set, be down a break in the third and fight through. I have to be more disciplined. I will work on it."
Ninth seed Caroline Wozniacki brushed aside Petra Martic of Croatia 6-1 6-0, ensuring the Dane has reached at least the third round of every major this year.
And 13th seed Nadia Petrova of Russia eased into the third round with a 6-4 7-6 (7-3) victory over France's Julie Coin.