Beijing - Rafa Nadal will return to the top of the men's world rankings after Tomas Berdych retired with a back injury during their China Open semi-final on Saturday.
Serb Novak Djokovic, who will lose top spot when the new rankings are announced on Monday, will meet Frenchman Richard Gasquet in the second semi-final.
Berdych, trailing 2-4 in the opening set, took a medical time out and returned to the court but after a few points decided he could no longer continue, handing the 27-year-old Spaniard an easy passage to Sunday's title round.
Nadal, who boosted his grand slam singles tally to 13 this year by winning the French and U.S. Opens, has not being ranked number one since July 2011 but has produced a stunning run since returning from a long injury lay-off in February.
He has lost two finals since his return, winning 10 tournaments and adding over $10 million in prize money in 2013.