Defending champion Roger Federer maintained his 100 percent record at this year's ATP World Tour Finals by completing his group fixtures with a 6-1, 3-6, 6-3 victory over America's Mardy Fish yesterday.

Roger Federer celebrates his win over Mardy Fish. PIC/AFP

Federer was already guaranteed top spot in Group B and a place in the semi-finals after winning his first two matches and the Swiss survived a mid-match wobble against Fish to extend his impressive run at London's O2 Arena.