ATP Tour Finals: Roger Federer sees off Juan Del Potro
Roger Federer sees off Juan Martin Del Potro 4-6 7-6 (7-2) 7-5 at the ATP Tour Finals in London, setting up a semi-final on Sunday against world number-one Rafael Nadal.
The Swiss trailed in all three sets but fought back from 3-0 down in the decider against fourth seed Del Potro.
Novak Djokovic faces Stanislas Wawrinka in Sunday's other semi-final.
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