MASON, Ohio – Rafael Nadal withdrew from the US Open Wednesday increasing concerns about the seriousness of the knee injury plaguing the 11 times grand slam winner. The Spanish world No. 3 has not played since suffering a shock second-round defeat by lowly ranked Czech Lukas Rosol at Wimbledon in June. Nadal missed the London Olympics because of a recurrence of tendinitis in his knees and subsequently withdrew from ATP Tour events in Toronto and Cincinnati. “I am very sad to announce that I am still not ready to play,” Nadal, the 2010 US Open champion, said in a statement. “I am sorry since I always found great crowds and great support, but I have to continue with my recuperation and preparation to be ready to play in the right conditions.” Nadal, whose aggressive and physical style has delighted crowds, has had frequent problems with both his knees.Andy Roddick's US Open preparations took a turn for the worst Tuesday when he suffered a back injury in a 7-6, 6-3 first round defeat by France's Jeremy Chardy at the Cincinnati Open. Chardy, who took his place in the first round as a ‘luck loser', triumphed 7-4 in a first set tie-break but Roddick struggled in the second set during which he had treatment for back spasms. After receiving attention, Roddick's serve was noticeably slower and he was broken twice by the Frenchman who is ranked 38th in the world. The back injury came when the American went for a low shot, he said. Chardy will take on Russia's Denis Istomin in the second round. There was better news, though, for another American with 10th seed Mardy Fish defeating Spaniard Feliciano Lopez 6-2, 6-2 in their first round game. German former world No. 2 Tommy Haas saved one match point to beat Argentine David Nalbandian 6-7, 7-6, 6-3 and the 34-year-old will next face Argentine sixth seed Juan Martin del Potro. Japan's Kei Nishikori cruised to a 6-1, 6-2 win over Spaniard Marcel Granollers in a match that lasted just 65 minutes. Russian-American Alex Bogomolov also wasted little time in beating Finn Jarkko Nieminen 6-4 6-3 to set up a clash with world No. 1 Roger Federer, a four-time winner at Cincinnati. In women's play, unseeded Olympic doubles champion Venus Williams found herself in a struggle with Russian Maria Kirilenko, the 12th seed, before pulling out a 6-3, 6-7 (5-7), 6-2 first-round win in nearly 2 1/2 hours. The 32-year-old American was helped by 11 aces but did not do herself any favors as she failed to serve out a straight-sets win. Williams was joined with a sloppy win by younger sister Serena as the second seed dispatched Eleni Daniilidou of Greece 6-3, 6-4 for a third-round place despite 44 unforced errors. US Open winner Samantha Stosur made heavy weather of a win over Anabel Medina Garrigues 6-3, 6-7 (6/8), 6-4 while Swede Johanna Larsson upset French eighth seed Marion Bartoli 6-4, 6-2. Russian Elena Makarova eliminated Nadia Petrova when her 15th-seeded compatriot trailed 7-6 (10/8), 3-1. Slovakia's Daniela Hantuchova fought back in the second set, surviving match point, to beat China's Zheng Jie 2-6, 7-6, 6-3 and will next face experienced Italian Sara Errani. The US Open in New York runs from Aug. 27 to Sept. 9. – Agencies