Samantha Stosur after her win over Elena Dementieva, in New York, on Sunday

New York: Two-time major champion Svetlana Kuznetsova double-faulted 10 times and was upset by 45th-ranked Dominika Cibulkova of Slovakia 7-5, 7-6 (4) in the fourth round of the US Open, on Monday.

Cibulkova reached her first quarter final at Flushing Meadows despite being treated by a trainer for a left leg problem between sets. She was the lowest-ranked of the 16 women in the fourth round.

In the men’s side, third-seeded Novak Djokovic rolled into his sixth straight Slam quarters, defeating Mardy Fish 6-3, 6-4, 6-1. Gael Monfils beat countryman Richard Gasquet 6-4, 7-5, 7-5 to give France its first US Open quarter finalist in a decade.

Andy Murray hobbled out of the tournament Sunday, beaten 6-7, 7-6, 6-3, 6-3 in the third round by Switzerland’s Stanislas Wawrinka after his ailing body and his mind failed him when he needed it most.

Struggling to run at full speed after requiring treatment to his legs, elbow and neck, the Briton appeared powerless to stop Wawrinka, who was battling his own injury problems but still played superbly, from pulling off the biggest upset of the championship.

Murray’s limp departure was in stark contrast to an incredible fightback from Australia’s Samantha Stosur, who saved four match points to beat Elena Dementieva 6-3, 2-6, 7-6 in a nail-biting centre court match that did not end until 1.35 am (local time), the latest finish for a women’s match at the US Open.

World No. 1 Rafa Nadal, playing before Murray’s defeat, sent an ominous warning to his rivals about his plans to complete his collection of Grand Slam titles in New York.

The Spaniard, getting better with each match on the back of a new and improved serve, overpowered France's Gilles Simon 6-4, 6-4, 6-2 to steam into the fourth round without dropping a single service game in three matches.

Venus Williams and Kim Clijsters passed their first real tests at Arthur Ashe Stadium with flying colours to safely book their places in the quarter finals.

The pair could hardly have been more impressive as they brushed past tricky opponents to remain on course for a blockbuster semi-final showdown when the season’s last Grand Slam enters its second week.

Williams, the champion at Flushing Meadows in 2000 and 2001, defeated Israeli 16th seed Shahar Peer 7-6, 6-3 in an ideal preparation for the more difficult matches ahead of her.

Clijsters, who won the title in 2005 and again last year, thrashed Serbia’s former world No. 1 Ana Ivanovic 6-2, 6-1 in just under an hour. Like Nadal and Williams, she is yet to drop a set in the championship.

Clijsters’ next opponent is Stosur, who is developing a reputation as one of the toughest players in women’s tennis.

She saved a match point to beat Serena Williams in the quarter finals of the French Open in June and another four in beating Sara Errani in New Haven last week.

Italy’s Francesca Schiavone, brimming with confidence after she beat Stosur in the final at Paris to capture her maiden Slam, also cruised through to the last eight, beating Russia's Anastasia Pavlyuchenkova 6-3, 6-0.

Spain are already assured of at least one men’s semi-finalist after Fernando Verdasco, David Ferrer and Felciano Lopez joined their countryman Nadal in the same section of the draw.

Nadal will face Lopez next with the winner to play either Ferrer or Verdasco.

Another two Spaniards, Albert Montanes and Tommy Robredo, are also through to the last 16, giving Spain a total of six, easily the most by any one country this year.

Wawrinka, seeded 25th, advanced to play Sam Querrey, the only American left in the men's competition, although the big winner could well be Nadal, who was drawn to face Murray in the semi-finals.

Murray’s loss was another disappointment for the Scotsman, who arrived at Flushing Meadows seeded fourth, in great form, and holding genuine hopes of ending Britain's 74-year wait for a men's Grand Slam singles champion.

Murray was at a loss to explain his lacklustre performance against Wawrinka, who teamed up with Roger Federer to win the Olympic gold medal in doubles with Roger Federer at Beijing in 2008.

Murray had sailed through his first two matches and looked to be heading to another victory when he won the first set tiebreaker then served for the second set when all of a sudden his game fell apart at Louis Armstrong Stadium.

By the start of the third set he was clearly in discomfort and protecting his left thigh but did not ask for a medical timeout and allowed his frustrations to effect his game.

There was good news for India on Sunday. Rohan Bopanna and his Pakistani partner Aisam-ul-Haq Qureshi advanced to the men’s doubles quarter finals with an upset win over second-seeded Canadian-Serbian pair of Daniel Nestor and Nenad Zimonjic here.

The Indo-Zimbabwean pair of Leander Paes and Cara Black also advanced to the last-eight stage of the tournament in the mixed doubles event.

The 16th seeded Indo-Pak pair of Bopanna and Qureshi streamrolled their opponents 6-3, 6-4 in a one-sided pre-quarter final clash at Flushing Meadows here.

Both Bopanna and Qureshi were on song with their trademark aggressive serves and precision forehands as the duo demolished the Grand Slam contenders in straight sets.

They will next face the daunting South African-Belgian pair of Wesley Moodie and Dick Norman, who reached the semi-finals of the French Open and Wimbledon this year. This will be the second consecutive appearance at a Grand Slam quarter final for the Indo-Pak pair who made it to the final eight at the Wimbledon.

In the second round of the mixed doubles event, second seeded Paes and Black lived up to their billings, defeating unseeded Estonia-Swedish pair of Kaia Kanepi and Robert Lindstedt 6-1, 6-4.

They will next meet Anna-Lena Groenefeld of Germany and Mark Knowles of Bahamas in the third round.

Day VIi results
Seeded players & indians only
Men’s singles, Round III: Rafael Nadal (1, Esp) bt Gilles Simon (Fra) 6-4, 6-4, 6-2; Fernando Verdasco (8, Esp) bt David Nalbandian (31, Arg) 6-2, 3-6, 6-3, 6-2; David Ferrer (10, Esp) bt Daniel Gimeno-Traver (Esp) 7-6 (2), 6-2, 6-2; Mikhail Youzhny (12, Rus) bt John Isner (18, US) 6-4, 6-7 (7), 7-6 (5), 6-4; Sam Querrey (20, US) bt Nicolas Almagro (14, Esp) 6-3, 6-4, 6-4; Feliciano Lopez (23, Esp) bt Sergiy Stakhovsky (Ukr) 6-3, 4-0, retired; Stanislas Wawrinka (25, Sui) bt Andy Murray (4, GBR) 6-7 (3), 7-6 (4), 6-3, 6-3
Women’s singles, Round IV: Kim Clijsters (2, Bel) bt Ana Ivanovic (Srb) 6-2, 6-1; Venus Williams (3, US) bt Shahar Peer (16, Isr) 7-6 (3), 6-3; Sam Stosur (5, Aus) bt Elena Dementieva (12, Rus) 6-3, 2-6, 7-6 (2); Francesca Schiavone (6, Ita) bt Anastasia Pavlyuchenkova (20, Rus) 6-3, 6-0
Men’s doubles, Round III: Rohan Bopanna/Aisam-ul-Haq Qureshi (16, Ind/Pak) bt Daniel Nestor/Nenad Zimonjic (2, Can/Srb) 6-3, 6-4
Mixed doubles, Round II: Cara Black/ Leander Paes (2, Zim/Ind) bt Kaia Kanepi/Robert Lindstedt (Est/Swe) 6-4, 6-1