LONDON (AP) -- Six-time champion Roger Federer rallied past Juan Martin del Potro 4-6, 7-6 (2), 7-5 Saturday to reach the semifinals of the ATP World Tour Finals for an 11th time.
Federer will face top-ranked Rafael Nadal on Sunday, and Novak Djokovic will take on newcomer Stanislas Wawrinka in the other semifinal at the year-end tournament.
Federer and del Potro needed a win in their final round-robin match to advance from Group B.
Only once in 12 appearances has Federer failed to reach the final four. The 17-time Grand Slam winner has struggled this season, and the event featuring the top eight players is his last chance to win a big title in 2013.