Juan Martin del Potro beats Roger Federer

Juan Martin del Potro has beaten top seed Roger Federer to reach the semi-finals of the ATP World Tour Finals.



Del Potro’s win has effectively knocked out Andy Murray.



However Federer is still in contention.



Federer knew that a win of any kind would put him through with Murray, while Del Potro needed a straight-sets win to qualify.



Del Potro won 6-2, 6-7, 5-7, 6-3 to take himself and Federer through and leave Murray helpless as it came down to the percentage of games won by all three men.



The qualification system deemed very confusing left Del Potro waiting in the O2 Arena to find out if he had made it.



When it was finally revealed he had gone through to the last four, Del Potro said it was an incredible moment.



Murray had earlier missed his opportunity to guarantee qualification with a straight-sets win over Fernando Verdasco, the Briton needing three sets before eventually battling past the Spaniard.