ATP Tour Finals: Del Potro upsets Federer to qualify
Juan Martin del Potro upsets two-time defending champion Roger Federer to join the Swiss in the last four of the ATP World Tour Finals.
Del Potro's 7-6 (7-3) 4-6 6-3 victory means both he and Federer qualify for the semi-finals, alongside world number one Novak Djokovic and Andy Murray from Group A.
The big-serving Argentine's victory came despite his only creating one break point in the match, with Federer only able to convert one of his four.
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