London, Nov 9 (IANS): World No. 1 Rafael Nadal defeated Tomas Berdych for the 16th straight time to qualify for the semi-finals from Group A with a perfect 3-0 record at the ATP World Tour Finals here Friday.

Nadal, who had already sealed his berth, helped seventh seed Stanislas Wawrinka of Switerland to qualify for the semi-finals. Berdych needed to beat Nadal to ensure his spot in the last four, reported Xinhua.

"Stan came to the locker room and said good luck. I said I would try my best. It's a good result for Stan. He's good friend of mine," said Nadal.

Nadal completed a 6-4, 1-6, 6-3 victory over Berdych in one hour and 50 minutes. The win means that he will face fourth seed Juan Martin del Potro or sixth seed and six-time former champion Roger Federer in the semi-finals Sunday.

In the day's other match, Wawrinka fought back from one set down to beat third seed David Ferrer 6-7 (3-7), 6-4, 6-1.

Ferrer, 31, who lost all three matches, 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 has won 10 titles from 13 finals since returning from a seven-month injury lay-off in February. He has compiled a 23-4 record against Top 10 opponents in the ATP Rankings.