LONDON (AP) -- Stanislas Wawrinka upset No. 3 David Ferrer 6-7 (3), 6-4, 6-1 Friday at the ATP World Tour Finals, maintaining the chance to reach the semifinals.
Wawrinka had 35 winners, including 12 aces, to clinch his second win at the elite year-end tournament. He'll need top-ranked Rafael Nadal to beat Tomas Berdych in the evening match to advance to the final four.
''For sure, I'm going to be a big fan of Rafa,'' said No. 8 Wawrinka, who is enjoying a breakthrough season after years in the shadow of Swiss star Roger Federer. ''I did my job all week. I did the best I can, so now I'm just going to watch what is going to happen and I'll be really happy if Rafa wins tonight.''
Nadal, who clinched the season-ending No. 1 ranking this week, has already qualified from Group A after winning his first two matches without losing a set.
Defending champion Novak Djokovic has won Group B. The winner of Saturday's match between Juan Martin del Potro and Federer will join him in the semifinals.
Two unforced errors by Ferrer in the first game of the third set gave Wawrinka an early break, and the U.S. Open semifinalist hit three aces in the next game for a 2-0 lead.
Wawrinka broke again for a 4-1 lead and closed out the match with a backhand after Ferrer misplayed an easy volley.