The Spaniard was due to make his first appearance since retiring in the US Open semi-finals in September at the Masters 1000 event in the French capital.

Nadal, a 17-time Grand Slam champion, withdrew due to an abdominal injury and did not face compatriot Fernando Verdasco in round two.

Serbia's Djokovic, a 14-time Grand Slam winner and four-times a champion in Paris, will now replace Nadal as world number one when the new rankings are released on Monday (November 5).

Elsewhere today, Switzerland's Roger Federer, the 2011 winner, made it through without hitting a ball at the AccorHotels Arena.

The 20-time Grand Slam champion and third seed was due to play Milos Raonic but the Canadian pulled out due to an elbow injury.

In other matches today, American defending champion Jack Sock progressed to round three.

The 16th seed knocked out France's home hope Richard Gasquet 6-3, 6-3.

South Africa's Wimbledon runner-up Kevin Anderson came through three sets to knock-out Georgian Nikoloz Basilashvili.

Anderson, seeded seventh, won 6-3, 6-7, 7-6.

German fourth seed Alexander Zverev was another to go through as he beat American Frances Tiafoe 6-4, 6-4.

The Paris tournament is the last before the season-ending ATP Finals in London, which begin on November 12.

The final in the French capital, the host of the 2024 Olympics and Paralympics, will be held on November 4.