In the Australian Open Tennis tournament at Melbourne, Roger Federer of Switzerland advanced to the semi finals of men's singles defeating Argentine Juan Martin del Potro. The 16-time grand slam winner Federer shocked the Argentine, Del Potro 6-4, 6-3, 6-2.In another encounter, a fired-up Rafael Nadal of Spain survived a huge scare from big-hitting Czech Tomas Berdych to prevail 6-7, 7-6, 6-4, 6-3. Nadal will clash with Roger Federer in the semi finals. In Women Singles, defending champion Kim Clijsters advanced to the semi finals. Belgian Clijsters ousted the 21-year-old top seed Caroline Wozniacki of Denmark, 6-3, 7-6, 7-4.Clijsters ended Dane controversial reign as world number one with a straight-sets win in the quarter-finals.By failing to reach the last four, Wozniacki is guaranteed to lose her number one ranking to Azarenka, Petra Kvitova or Maria Sharapova when the new standings are released next Monday.In another encounter, third seeded Victoria Azarenka of Belarus advanced to the semi finals beating Agnieszka Radwanska of Poland 6-7, 6-0, 6-2.In women's doubles, Indo-Russian pair of Sania Mirza and Elena Vesnina shocked second seeds Americans pair of Liezel Huber and Lisa Raymond to breeze into the semifinal of the Australian Open on Tuesday.They defeated Americans for a 6-3, 5-7, 7-6 in the marathon quarter-final, which lasted three hours and five minutes.This is only the second time in Sania's career that she has reached a Grand Slam semi-final in the women's doubles event. In 2011, she had reached the Wimbledon semis with Elena, losing to Kveta Peschke and Katarina Srebotnik.Sania and Elena will now fight it out with the Russian combo of Svetlana Kuznetsova and Vera Zvonareva for a place in the summit clash.