London, Nov 9 (IANS): Stanislas Wawrinka fought back from one set down to beat third seed David Ferrer and keep alive his hope of qualifying for the semi-finals at the ATP World Tour Finals here Friday.

Wawrinka, ranked eighth in the world and making his debut in the season-end event, will qualify if Rafael Nadal beats Tomas Berdych in the last Group A match, reported Xinhua.

The 28-year-old Swiss won the match 6-7 (3-7), 6-4, 6-1 over an apparently tired Ferrer, who was playing his 84th match of the year, more than anyone else on the ATP tour.

Ferrer, 31, said, "I played a lot of tournaments. I played seven tournaments in seven weeks."

He added: "I made the final in Stockholm, final in Valencia, final in Paris, and three matches here. It's too much. But now I know it's too much. Before, I never knew it. I made three finals in three weeks."

Nadal and Novak Djokovic have already qualified, with Juan Martin Del Potro and Roger Federer to play for the final place Saturday.