Olympic Games Men’s singlesNishikori bt Ferrer 6-0, 3-6, 6-4Isner bt Tipsarevic 7-5, 7-6Del Potro bt Simon 6-1, 4-6, 6-3Women singles resultsWozniacki bt Hantuchová 6-4, 6-2Sharapova bt Lisicki 6-7, 6-4, 6-3Azarenka bt Petrova 7-6, 6-4Kerber bt Williams 7-6, 7-6Kvitová bt Pennetta 6-3, 6-0Williams bt Zvonareva 6-1, 6-0LONDON – Roger Federer moved into the Olympic quarter-finals with minimum fuss on Wednesday, while his gold medal rivals Novak Djokovic and Andy Murray had to dig deep to avoid third round exits.After securing a record-equalling seventh Wimbledon title, Federer is desperate to complete a career ‘Golden Slam’ by winning singles gold for the first time.The 17-time grand slam singles champion saw the defence of his doubles title with Stanislas Wawrinka fall apart with a 1-6, 7-6 (7/5), 6-3 loss to Israel’s Jonathan Erlich and Andy Ram.But Federer stayed on course for the singles with a 7-5, 6-3 win over Uzbekistan’s Denis Istomin on Wimbledon’s Court One.Federer, 30, will play John Isner for a place in the semi-finals after the American 10th seed defeated Serbian seventh seed Janko Tipsarevic 7-5, 7-6 (16-14)."I started really well and went into the lead 3-0. But he came back and I was a little bit shaken up I guess,” Federer said.World number two Djokovic, scheduled to face Federer in the Olympic final, endured a much tougher test as he came from behind to beat Australian veteran Lleyton Hewitt 4-6, 7-5, 6-1.Next up for the 2011 Wimbledon champion is French fifth seed Jo-Wilfried Tsonga, who beat Spain’s Feliciano Lopez 7-6 (7/5), 6-4.Britain’s Andy Murray also survived a stern examination from Cyprus’s Marcos Baghdatis before coming through 4-6, 6-1, 6-4.