Roger Federer staged a superb fightback to reach the semi-finals of the ATP World Tour Finals with a 4-6, 7-6 (7/2), 7-5 victory over Juan Martin del Potro on Saturday. Federer had only once failed to reach the last four in 11 previous appearances at the prestigious season-ending event and he recovered from a set and a break down, and then 3-0 down in the final set, to subdue the Argentine fourth seed and maintain his impressive record.
The six-time Tour Finals champion qualified in second place in Group B behind Novak Djokovic and will face world number one Rafael Nadal in Sunday's semi-finals at London's O2 Arena.