Rafael Nadal will supplant Novak Djokovic atop the rankings after advancing to the final of the China Open yesterday when Tomas Berdych of the Czech Republic retired with a back injury.
The Spaniard was a break up at 4-2 in the opening set of their semi-final when Berdych retired soon after taking an injury timeout.
Djokovic still has a chance to claim superiority as the two will meet in today's final, after the defending champion earned a comfortable 6-4, 6-2 victory over fifth-seeded Frenchman Richard Gasquet in the other semi-final.
Nadal, who improved to 27-0 on hard courts this season, will return to the top ranking for the first time since July 2011. Djokovic has been No. 1 for 101 weeks.
"The personal satisfaction is not because I am No. 1 today, it's because (of) all the work (I put in) to be where I am today," Nadal said. "I don't feel (like) a better player now than five hours ago, and I won't go to bed tonight feeling that I am the best player in the world - that's something I've never thought."
Djokovic, who is looking for his fourth title in five years at the China Open, won his match in 80 minutes to improve his record to 9-1 against Gasquet.
In the women's draw, top-ranked Serena Williams and Jelena Jankovic of Serbia advanced to the final with contrasting wins.
Serena earned a straight-forward 6-2, 6-2 victory over Agnieszka Radwanska of Poland while Jankovic rallied for a 6-7 (7), 6-1, 6-1 win over Petra Kvitova of the Czech Republic.
Nadal had been assured of reclaiming the top spot if he reached the final in Beijing or Djokovic failed to defend his title.