Nadal has pulled out of the final tournament of the regular season due to an abdominal injury, meaning the Serbian ends his two-year absence from the top of the pile when the new list is published on Monday.
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 revealed whether he will play in next week’s ATP Tour Finals in London.
He said in a press conference in Paris: “I arrived here a couple of days ago, as everyone knows I have been outside of the competition since the US Open.
“I took time off, I came back and it was great to be in Paris for a couple of days and practise with the guys.
“I enjoyed it, I feel, in terms of tennis, better than what I thought one week ago, but in the last few days I started to feel a little bit abdominal (pain), especially when serving. I checked with the doctor and the doctor recommended I did not play.”
In the early action on Wednesday, Kei Nishikori and John Isner kept their hopes of gatecrashing the Tour Finals alive with victories.
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 booked his place in the next round with a 6-4 6-4 win over Frances Tiafoe.
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