seeded Novak Djokovic overcame hip, ankle and stomach ailments to outlast Tommy Robredo 4-6, 6-2, 6-3, 5-7, 6-3 and reach the quarterfinals at the US Open on Tuesday. Luxembourg's 130th-rated Gilles Muller became the first qualifier since 2000 to reach a Grand Slam quarterfinal with a shocking upset of Russian fifth seed Nikolay Davydenko. Muller defeated Davydenko 6-4, 4-6, 6-3, 7-6 (12-10) after three hours and seven minutes on a net cord volley winner, prompting the Russian to slam his racquet to the court in frustration. Muller will next play the winner of a later match bewteen four-time defending US Open champion Roger Federer and Russia's Igor Andreev. Known for his impeccable impersonations of fellow pros, Djokovic gave a real-life imitation of someone who plays his best when hurt. “If I start talking about the things that are bothering me now, we can talk till tomorrow,” he said. Djokovic twice called for a doctor, and looked to be in serious trouble when he went to a fifth set against the extremely fit Spaniard. But with the score 2-all, the No. 15 Robredo tumbled onto the hard court while chasing a shot, and lost his zip. Runner-up at the last US Open and the Australian Open champion this year, Djokovic next takes on either No. 8 Andy Roddick or No. 11 Fernando Gonzalez. “Whoever I play will be physically fitter than me, that's for sure,” Djokovic said. Earlier, fifth-seeded Elena Dementieva reached the semifinals, beating No. 15 Patty Schnyder 6-2, 6-3 in another one of tennis' most-played matchups. Djokovic is developing a history of becoming hurt at major tournaments. He quit because of an infected blister on a toe while trailing Rafael Nadal in a 2007 Wimbledon semifinal. He also stopped after losing the first two sets of his 2006 French Open quarterfinal against Nadal, citing a back injury, and retired during his second-round match of the 2005 French Open. Djokovic struggled midway through this match and seemed to grow frustrated. At one point, he slung his racket after a missed shot, drawing boos and whistles from the Arthur Ashe Stadium crowd. Noted for bouncing the ball up to 30 times before serves, he sped up his routine as the match went on, trying to get off the court quickly. On a sunny afternoon with temperatures in the high 80s F (high 20s C), Djokovic had enough energy in the end to raise his record to 8-3 in five-set matches. Robredo fell to 9-4 in them. While crowds at Flushing Meadows pressed around the practice courts to watch Serena Williams and Venus Williams warm up for their 17th career meeting on Wednesday, Dementieva defeated Schnyder in their 17th contest. “Every time it's different,” Dementieva said, now 10-7 lifetime against her Swiss opponent. After winning the Olympic gold medal and becoming a semifinalist at Wimbledon, Dementieva kept up her best run ever. She improved to 10-0 in sets at this tournament and next plays either No. 2 Jelena Jankovic or No. 29 Sybille Bammer. Dementieva beat Schnyder for the fourth straight time, including three victories this season, in a pairing that started in 1997. Neither has won a Grand Slam, no match for the 15 combined major titles by the Williams sisters. The Russian star made it to the final of the 2004 US Open, but her often-shaky serve deserted her and she got swept by Svetlana Kuznetsova. Dementieva did much better this time, putting 80 percent of her first tries in play. She also was much more steady, making only 14 unforced errors to Schnyder's 29. “I think the serve was the key,” Dementieva said. On Monday, the Williams sisters confirmed holding another family reunion on center court at the US Open after registering wins that set up a tiebreaking, sibling clash in the quarterfinals at Flushing Meadows. Fourth seed Serena routed French wildcard Severine Bremond 6-2, 6-2, while seventh-seeded elder Venus crushed Agnieszka Radwanska of Poland 6-1, 6-3 to book the rendezvous. British sixth seed Andy Murray, 21, also stormed into the quarters for the first time with a 6-1, 6-3, 6-3 demolition of Swiss 10th seed Stanislas Wawrinka. - AP __
