BEIJING (AP) -- Rafael Nadal was assured of taking the No. 1 ranking from Novak Djokovic after advancing to the final of the China Open on Saturday 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 semifinal when Berdych retired soon after taking an injury timeout.
Djokovic, the defending champion, earned a comfortable 6-4, 6-2 victory over fifth-seeded Frenchman Richard Gasquet in the other semifinal.
Even if he loses to Djokovic in the final Sunday, Nadal will still sit atop the rankings.
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.
Nadal, the reigning French Open and U.S. Open champion, has had a dominant year since returning in February from a seven-month layoff due to a left knee injury. He has won 10 titles and reached 12 finals overall, compiling an ATP Tour-best record of 65-3 on the season.
He hasn't lost a match since falling in the opening round at Wimbledon to 135th-ranked Steve Darcis of Belgium in June, his only blip this year.
''(This is) a great year, one of the best years of my career without any doubt,'' Nadal said. ''Sure is special (to) be back to the top position of the rankings after more than a half year without playing tennis.''