Djokovic lost the number three ranking in May
Novak Djokovic beat Fernando Verdasco to reach the semi-finals of the China Open and move within one win of Andy Murray's world number three ranking.
The Serb, 22, came through 6-3 1-6 6-1 against fifth seed Verdasco at the Olympic tennis centre, and will next face Robin Soderling in the last four.
Rafael Nadal beat Marat Safin 6-3 6-1 and will play Marin Cilic, who upset fourth seed Nikolay Davydenko 6-4 6-4.
Svetlana Kuznetsova made it through to the last four of the women's event.
The Russian sixth seed beat compatriot Anastasia Pavlyuchenkova 6-3 6-3 and will next meet 13th seed Nadia Petrova, who defeated Peng Shuai 6-7 (5-7) 6-3 6-2.
"I'm very happy to get through even though I didn't really start out playing well, but I really picked it up by the second and third sets," said Petrova, who beat Serena Williams on Thursday.
"It's always difficult to come out the next following day and put on the same performance."
In the other half of the draw, Poland's Agnieszka Radwanska beat fourth seed Elena Dementieva 7-5 6-3.
France's Marion Bartoli beat seventh seed Vera Zvonareva of Russia 3-6 7-5 6-2 in the day's final quarter-final.
Murray's withdrawal from next week's Shanghai Masters because of a wrist injury means Djokovic just has to reach the final in Beijing to move above the Scot in the rankings on 19 October.
"I was surprised when he pulled out of Shanghai but obviously he has some problem with injury," said Djokovic.
"That's tennis. Rankings come and go, we are all quite close and it can turn around at any time. It's still not the end of the year."
Djokovic will face Soderling in the last four after the Swede beat Ivan Ljubicic 7-6 (7-3) 6-4.