Nadal was pushed to the brink before he defeated the local favorite and fifth seeded Andy Murray of Great Britain 7-6(7-5), 3-6, 7-6(8-6).

After the three hour match, Nadal admitted to fatigue.

“Seriously I was a little bit tired in the second set,” he said. “I don’t know what’s going to happen tomorrow, how I’m going to feel. You can imagine, right now, I am very tired.”

In January, Federer took the first of four grand slams titles to be contested this year at the Australian Open. But then Nadal swept the remaining three, winning the French Open, Wimbledon and the US Open back to back in a breathtaking display of power tennis.

Federer, who has won a male record of 16 singles grand slam titles, is considered by many to be the greatest tennis player ever.

However head to head Federer trails Nadal 14-7. Nadal, who has won nine singles grand slams titles, since 2008 has defeated Nadal in five of their last six matches.

In the duo’s last meeting on clay in the spring of this year in the final of the ATP World Tour Masters 1000 Madrid, Nadal beat Federer 6-4, 7-6(7-5).

Federer after his semifinal round win acknowledged the challenge of facing the Spaniard.

“Obviously I’m really looking forward to playing against Rafa tomorrow. Who wouldn’t?” said Federer.

“What he’s achieved is amazing. He’s proven himself that he can play on any surface now.”

Looking forward to 2011, should Nadal win the Australian Open in January, he would become the first person since Serena Williams of the USA in 2003 to hold all four grand slam singles titles simultaneously.