London, Nov 24 (IANS): Spain's David Ferrer thrashed world No.1 Novak Djokovic in straight sets, earning a semi-final berth at the Barclays ATP World Tour Finals.

Ferrer, ranked No.5 in the world, took all his serve games and broke twice in each set, beating Djokovic 6-3, 6-1 in 76 minutes here Wednesday.

Ferrer became the second player to reach the semi-finals after Swiss maestro Roger Federer grabbed his spot with two wins in Group B Tuesday.

"I am very motivated. I am in the semi-finals. I want to enjoy this moment. I don't want to think about the semi-final on Saturday," Ferrer was quoted as saying by Xinhua.

Djokovic, who clinched 10 titles including three Grand Slams this season, made 33 unforced errors in the match, said he had no words to explain the defeat.

"It was the worst match I've played this season so far, definitely," said the Serbian. "So many unforced errors. I'm not playing well. That's a fact."

Coming to London with a 69-4 record this season, Djokovic fought hard to edge out world No. 7 Tomas Berdych 3-6, 6-3, 7-6(3) in his opening match Monday.

"I wasn't on my best in the first match, but I managed to kind of get into the rhythm in the second set," said the 24-year-old. "This match, I have no words to explain. Nothing was going well."

Djokovic will face countryman Janko Tipsarevic in his last group A match after the world No.9 replaced injured Andy Murray to join the competition from the second round and lost a close match to Berdych 6-2, 3-6, 6-7(6).

"There is still a chance," said Djokovic. "But if I don't play at least 50% better than I did tonight. I don't think I will have any chance."