LONDON, July 12 (Xinhua) -- No. 1 seed Roger Federer was edged out by South Africa's Kevin Anderson 2-6, 6-7, 7-5, 6-4, 13-11 in a 4h 14min thriller, with the Swiss missing the chance to claim his ninth Wimbledon title this year.

The 36-year-old had a solid opening as he took the first two sets and arrived at match point in the third. It looked as if the Swiss was on his way to a straight sets win, but Anderson changed the whole story, saving match point and claiming the third set in the prelude to an epic comeback victory.

"At 2-0 down I tried my best to keep fighting. I kept telling myself to keep believing. I said today is going to be my day," said Anderson.

He impressed the crowd with his resilence and powerful serves, dragging the match to the final set, in which Federer was deeply troubled by unforced errors.

It finally took Anderson 24 games to upset the eight-time champion and make it to his first semifinal at the All England Club. The 32-year-old is also the first South African to progress to the last four at Wimbledon since 1983.

Although frustrated by the defeat, Federer was generous with his praise of Anderson.

"I think I had my chances, so it's disappointing. No doubt about it, he was consistent, he was solid. He got what he needed when he had to. Credit to him for hanging around that long," Federer said.

Anderson will take on another newcomer at this stage, John Isner, in the semifinals. The No.9 seed beat Milos Raonic 6-7, 7-6, 6-4, 6-3 in the quarters.

The other semifinal will take place between old rivals Rafael Nadal and Novak Djokovic.

World No.1 Nadal triumphed in a 4h 48min epic against Juan Martin Del Potro. Dropping his first two sets at this year's tournament in the second and third, the Spaniard bounced back from 2-1 down and bested Del Potro 7-5, 6-7, 4-6, 6-4, 6-4 to advance into the semifinals, his first appearance in the last four at Wimbledon since 2011.

"I think it was great quality tennis and in the final set there were some amazing points," said Nadal afterwards, "Anything could have happened, so this is a big achievement for me to get to the semi-finals at Wimbledon."

Meanwhile, Djokovic did not take long to beat Kei Nishikori 6-3, 3-6, 6-2, 6-2 to reach his first Grand Slam semifinal in over two years.

Nadal and Djokovic will face off on Friday for a place in the final.

Wimbledon also welcomed many familiar faces in the invitational events on Wednesday. China's Li Na paired with Ai Sugiyama of Japan in the women's doubles but suffered a 6-4, 6-1 loss to her old friend Kim Clijsters of Belgium and her partner Rennae Stubbs.