Roger Federer lost to Juan Martin del Potro for the second time in three weeks when he went down to the Argentine 7-6 (3), 4-6, 6-3 in his last round-robin match here at the ATP World Tour finals in a result that ensures del Potro will join Federer, Novak Djokovic and Andy Murray in Sunday's semifinals.
No champion enjoys losing but Federer was determined not to get upset by this one or by the fact that, unlike Murray and Djokovic, he will be playing three consecutive days while they have had a day off.
"No, no problems," he said when asked about his physical condition. "I'm not worried. It's important to move on right now. Obviously I'm excited to be in the semis and hopefully play a good match."
Having admitted that it was his inability to make much impression of the Argentine's huge serve that caused his downfall, Federer went on to talk about the mental aspects of playing in a situation where winning is not paramount but the result coul...