Nadal has pulled out of the final tournament of the regular season due to an abdominal injury, meaning the Serbian will end his two-year absence from the top of the pile when the new list is published on Monday.
Djokovic, who has won Wimbledon and the US Open in the last four months, was memorably disposed as world No 1 by Andy Murray in the French capital in 2016.
Nadal has not played since the US Open in September, when he suffered a knee injury in the semi-final and his comeback has been now been curtailed. The Spaniard has not said whether he will play in next week’s ATP Tour Finals in London.
Kei Nishikori and John Isner kept their hopes of gatecrashing the Tour Finals alive with victories in Paris. Nishikori beat Frenchman Adrian Mannarino 7-5, 6-4 while Isner battled past Mikhail Kukushkin 6-3, 6-7 (2), 7-6 (1). Fourth seed Alexander Zverev beat Frances Tiafoe 6-4, 6-4.
l Garbine Muguruza survived a scare as she opened her WTA Elite Trophy campaign in Zhuhai with a battling 3-6, 6-3, 6-2 win over Zhang Shuai.