Roger Federer saved four match points before winning a thrilling all Swiss semi final against Stan Wawrinka at the ATP World Tour Finals championship. The six time champion wrestled control from his compatriot and came through 4-6, 7-5, 7-6 in London. Second seed Federer will take on world number one Novak Djokovic who beat Kei Nishikori 6-1, 3-6 and 6-0 in today's final.