<div><p>Andy Roddick's hopes of a second US Open crown, six years after his first, were blown apart by giant compatriot John Isner in the first major upset of the men's tournament.</p><p>The six-foot-nine-inch (2.03m) product of the US collegiate system stunned the fifth seed and top US hope 7-6 (7/3), 6-3, 3-6, 5-7, 7-6 (7/5) in a 3 hours 51 minutes, third-round clash between two of the biggest servers in tennis.</p><p>There were scares also for top seed and defending champion Roger Federer and fourth seed Novak Djokovic. Both dropped their opening sets but both bounced back to win in four.</p><p>While defending champion and top seed Federer made it 14 in a row over former world No.1 Lleyton Hewitt with a 4-6, 6-3, 7-5, 6-4 win, fourth-seeded Djokovic struggled to see off the challenge of US wildcard Jesse Witten 6-7 (2/7), 6-3, 7-6 (7/2), 6-4.</p><p>The Isner-Roddick clash turned on two tie-breaks - one in the first and one in the fifth. Both were won by 24-year-old Isner, who is back to full fitness after missing three months of the year with mononucleosis.</p><p>"Maybe I was a little bit fortunate to win tonight, but I played well and I think I deserved it," he said. "It hinged on a few points here and there.</p><p>"He brought it back and took it to the fifth set and from there it was anybody's game.</p><p>"I told myself, just hold serve, and if I could get to the tie-breaker I was confident.</p><p>"I can really do some damage here. I'm not finished yet."</p><p>With US No.2 Sam Querrey also going out in a 6-2, 7-5, 6-7 (6/8), 6-1 loss to French Open runner-up Robin Soderling of Sweden and James Blake losing 7-6 (7/2), 6-4, 6-4 to Tommy Robredo, Isner now represents the best chance of a first home win since Roddick in 2003.</p><p>It was a crushing blow for Roddick, who lost a marathon five-setter to Roger Federer in the Wimbledon final in July.</p><p>"It was a tough one to lose especially after coming back all that way," he said.</p><p>"Bottom line for the entire match is he played great in the breakers. I dont know if I missed a ball in one of the breakers. He played well when he had to.</p><p>Federer, seeking a sixth straight US title to match the 84-year-old record of Bill Tilden, was uncustomarily out first under a hot midday sun at the Arthur Ashe Stadium court and he was uncustomarily sluggish and careless.</p><p>In contrast, Hewitt, the champion here in 2001 who is clawing his way back up the rankings after falling out of the top 100 in February, looked much the livlier and more enterprising.</p><p>The Australian broke Federer twice to win the first set and had several break points in the third after the Swiss star had levelled the set scores.</p><p>But he failed to take them and Federer gradually worked his way back to near his very best, taking the third set and then breaking at start of the fourth.</p><p>A consummate front-runner, Federer raced away to clinch his 38th straight win at the US Open, including one walkover, since he lost to David Nalbandian in the fourth round in 2003.</p><p>The win, which assures Federer of retaining the world No 1 status no matter who wins the title here, means he will play Robredo for a place in the quarter-finals.</p><p>"It could have gone either way," Federer said.</p><p>"He had a good start and he believed maybe more today than in some of the other ones he played against me.</p><p>"The way I came through, I was very happy, because I knew that being down a set against Lleyton is always going to be a difficult situation for me to be in."</p><p>"Make one more mistake and I'm in the fifth set maybe, or I go down completely. So I was relieved coming through."</p><p>Djokovic, the 2008 Australian Open champion and 2007 US Open runner-up, took three hours and 28 minutes to subdue Witten, the longest long-shot still in the field at 276th in the world.</p><p>"Looking at that match, I don't know who was No. 4 in the world," Djokovic said. "It was a tough win. For either one it would have been well deserved."</p><p>Also through early on into the fourth round from the top half of the draw was wily Czech Radek Stepanek, who defeated Germany's Philipp Kohlschreiber 4-6, 6-2, 6-3, 6-3 to set up a clash with Djokovic.</p><p>Russian livewire Nikolay Davydenko, seeded eight, cruised past Switzerland's Marco Chiudinelli 6-4, 7-5, 7-5. and he will go up against Soderling.</p><p>Spanish 10th seed Verdasco meanwhile hit back from a break down in the final set to edge German veteran Tommy Haas 3-6, 7-5, 7-6 (10/8), 1-6, 6-4.</p><img src="http://admatch-syndication.mochila.com/images/ad.gif?aid=58158915&bid=informcom" /></div><div id="copyright"><div>

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