The first men's singles semi-final in the Wimbledon Tennis Championsips is now in progress in London between defending champion Novak Djokovic and six-time winner Roger Federer. It is the first clash on grass between the two stars in their six-year rivalry. Federer was leading 3-2 in the first set when reports last came in.In other semi-final of the men's singles, Jo-Wilfried Isonga of France faces Andy Murray of Great Britain.For India, Veteran Leander Paes is the lone player left in fray in the championships. Paes advanced to the mixed doubles quarterfinals with his Russian partner Elena Vesnina. The fourth seeded pair overcame the Belarussian combination of Max Mirnyi and Victoria Azarenka in straight sets 7-6, 6-3. They are now up against the Australian-Russian pairof Paul Hanley and Alla Kudryavtseva in the quarterfinals.