The 27-year-old Spaniard was leading fourth seed Tomas Berdych 4-2 in the first set of their semi-final when his Czech opponent retired with a back injury.
“This is a great year, one of the best of my career,” said Nadal, who won the French Open and US Open and was last top of the rankings in July 2011.”
He continued: “The personal satisfaction is not because I am No1 today, it’s because of all the work I put in to be where I am today.
“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 about.”
Djokovic has spent 101 weeks as world No1, with the Serb having been knocked off top spot in July 2012 by Roger Federer but returning to number one in November.
Nadal has not lost a match since he was beaten by Belgian No135 Steve Darcis in the first round at Wimbledon back in June and has won 65 of the 68 he has played this season.
Djokovic takes on Frenchman Richard Gasquet on Saturday for a place in the China Open final against Nadal.
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