Current top two Tennis players, Novak Djokovic and Roger Federer will lock horns today in the title clash of the season ending ATP World Tour Finals in London. In the semi-finals last night, while world number one Djokovic defeated Japan's Kei Nishikori, 6-1, 3-6, 6-0, world number two Federer edged past compatriot Stanislas Wawrinka, 4-6, 7-5, 7-6. Both, Djokovic and Federer have played each other 36 times, with the Swiss leading 19-17. This includes a record 12 Grand Slam matches, tied with Djokovic and Rafael Nadal. In the last year's World Tour Finals, Djokovic had defeated Federer in the group stage. Djokovic was the winner of that tournament. Meanwhile, in the Doubles section, America's top seeded Bryan brothers, Bob and Mike, will clash with seventh placed Croatian-Brazilian team of Ivan Dodig and Marcelo Melo for the title today.