US Open Men’s singles, 3rd roundKohlschreiber bt    Isner     6-4, 3-6, 4-6, 6-3, 6-4Tipsarevic     bt     Žemlja             6-4, 6-3, 7-5Wawrinka     bt    Dolgopolov         6-4, 6-4, 6-2Gasquet    bt     Johnson             7-6, 6-2, 6-3Ferrer     bt     Hewitt     7-6, 4-6, 6-3, 6-0NEW YORK - Novak Djokovic continued his stroll through the U.S. Open draw on Sunday while former champion Andy Roddick staved off retirement by winning in front of 20,000 of his new-found best friends at raucous Arthur Ashe Stadium.While Djokovic had a workmanlike 6-3 6-2 6-2 victory over Frenchman Julien Benneteau to reach the fourth round, the stadium turned rowdy watching Roddick’s 7-5 7-6 4-6 6-4 triumph over Italy’s Fabio Fognini.Third seed Maria Sharapova survived a scare against Russian compatriot Nadia Petrova to reach the quarter-finals, having trailed 2-0 in the deciding set before a 73-minute rain delay allowed her to regroup and march to a 6-1 4-6 6-4 victory. Other winners included top-seeded Belarusian Victoria Azarenka and defending champion Sam Stosur of Australia on the women’s draw and David Ferrer of Spain and Swiss Stanislas Wawrinka on the men’s side.The party continued at Flushing Meadows for Roddick, who has become a rock star since announcing on Thursday he would retire after the U.S. Open."I’m comfortable out there,” Roddick told reporters. "I’d be an idiot not to use the crowd right now. It’s a huge advantage. Each match is almost like it’s another memory. I’m certainly going to use them.”