NEW YORK – Chinese ninth seed Li Na was knocked out of the US Open in the third round Friday, losing 6-4, 6-7 (5/7), 6-2 to Britain's Laura Robson, who had beaten triple champion Kim Clijsters in the previous round. Robson becomes the first British woman to make the last 16 in New York since Jo Durie in 1991 and will face defending champion Samantha Stosur of Australia for a place in the quarterfinals. “It was really tough,” said Robson, who said she will maintain her positive approach when she faces Stosur. “I have nothing to fear.” The 18-year-old Robson, the youngest player in the world top 100 and the 2008 Wimbledon junior champion, showed few signs of nerves as she swept into the fourth round of a major for the first time. Defending champion Stosur and Spanish fourth seed David Ferrer advanced with straight-set victories. Stosur reached the fourth round with a 7-6 (7/5), 6-2 victory over US 31st seed Varvara Lepchenko while Ferrer moved into the third round by ousting Dutch qualifier Igor Sijsling 6-2, 6-3, 7-6 (14/12). Ferrer, a 2007 US Open semi-finalist in his best Grand Slam run, battled through five match points and denied the Dutchman on three set points in the tie-break before a lob winner and a victory after two hours and seven minutes when Sijsling netted a forehand. “He played very well in the third set,” Ferrer said. “I was pleased to get it done.” French 11th seed Marion Bartoli also advanced with a 6-2, 6-4 victory over compatriot Kristina Mladenovic. Andy Roddick celebrated his 30th birthday Thursday by announcing his retirement as Roger Federer, the great Grand Slam tormentor of the American, eased into the third round at the US Open. Top seed and five-time champion Federer reached the last 32 with an easy 6-2, 6-3, 6-2 win over Germany's Bjorn Phau and next faces Spain's Fernando Verdasco, whom he has beaten four times in four matches. Federer, bidding to become the first man to win six New York titles in the Open era, clinched the 90-minute match with his 15th ace after also firing 44 winners past the 32-year-old Phau, the world No. 83. “Andy's a great man,” Federer said. “I had some great battles with him for a long, long time and all the Wimbledon finals come to mind. We had some epic battles over the years. “But he got the last laugh – he beat me in Miami this year.” Two-time women's champion Venus Williams was knocked out, losing 6-2, 5-7, 7-5 to German sixth seed, and 2011 semifinalist, Angelique Kerber, who also knocked the American out of the Olympics. Kerber has now won a tour-leading 55 matches in 2012. “It was unbelievable, it was such a tough match and very close. Venus is such a great player and has won so many Grand Slam titles,” said Kerber, who benefitted from Williams committing 60 unforced errors. Defeat for seven-time Grand Slam title winner Williams meant 2012 was the first year in her career that she failed to get beyond the second round of any of the four majors. “She's playing great but I didn't help myself a lot,” said Williams. “I tried to be aggressive but it's hard to be aggressive when every shot you hit goes out.” Sister Serena, the three-time champion, won her 60th match at the US Open, advancing to the third round with a 6-2, 6-4 victory over Spain's Maria Jose Martinez Sanchez. Williams, the Wimbledon and Olympic champion, will next face Russia's Ekaterina Makarova, who beat her at the Australian Open this year. Second seed Agnieszka Radwanska, who was Wimbledon runner-up to Serena, almost suffered a fourth successive second-round exit before fighting back from a set and 3-1 down to beat Spain's Carla Suarez-Navarro 4-6, 6-3, 6-0. Radwanska will face Serb 30th seed Jelena Jankovic. French fifth seed Jo-Wilfried Tsonga, who reached the quarterfinals in 2011, was the highest men's seed to fall when he slumped to a shock 6-4, 1-6, 6-1, 6-3 defeat to unheralded Slovak Martin Klizan. The flamboyant, shot-making Frenchman had come into the final Grand Slam event of the season in a fog of injury and form worries, summed up by having to skip the Cincinnati event after cutting his knee on a fire hydrant. “Today I was not in good shape. I didn't play good tennis,” said the 27-year-old Tsonga. Left-hander Klizan, the world 52, progressed to the third round of a Grand Slam for the first time and will tackle 32nd seed Jeremy Chardy of France. Men's sixth seed Tomas Berdych eased past Estonia's Jurgen Zopp 6-1, 6-4, 6-2 and faces America's Sam Querrey next. Spanish 11th seed Nicolas Almagro fought back to beat Philipp Petzschner 6-3, 5-7, 5-7, 6-4, 6-4 with the German's challenge undone by 62 unforced errors. American 23rd seed Mardy Fish, a quarter-finalist in 2008, beat Russia's Nikolay Davydenko, a semifinalist in 2006 and 2007, in a gruelling five-setter. His 4-6, 6-7 (4/7), 6-2, 6-1, 6-2 win was the 10th comeback victory from two sets-to-love down in the men's tournament this year. The 32-year-old men's wildcard James Blake wound back the clock to beat 24th seed Marcel Granollers 6-1, 6-4, 6-2. — Agencies