Roger Federer the six – time champion this evening saw off the of the young talented German Alexander Zverev 7-6 5-7 6-1 to book his place in the semi – finals of the ATP Finals in London. Zverev the third seed can still reach the last four if he wins against American Jack Sock on Thursday. Sock earlier today defeated fifth seed Marin Cilic 5-7 6-2 7-6, which ended the Croatian hopes of progressing further.