Defending champion Roger Federer kept his perfect record intact at the Barclays ATP World Tour Finals this year with a 6-1 3-6 6-3 victory over Mardy Fish at the O2 Arena.

Fourth seed Novak Djokovic reached the third round at Wimbledon with a straight-sets victory over battling German qualifier Simon Greul.

Rafael Nadal hit back from a set down against Mardy Fish to secure a place in the semi-finals of the US Open for the first time in his career.