Rafael Nadal has withdrawn from the Paris Masters with an abdominal injury.
It means Novak Djokovic, 31, will replace him as world number one when the rankings are released on Monday.
Earlier on Wednesday, Roger Federer made it through to the last 16 without playing when Milos Raonic pulled out with an elbow injury.
Nadal’s opponent, 34-year-old Fernando Verdasco, will play Jack Sock in the next round after the American beat France’s Richard Gasquet 6-3 6-3.
Earlier, Kei Nishikori had a straightforward 7-5 6-4 victory over Adrian Mannarino and John Isner served up 33 aces as he beat Mikhail Kukushkin 6-3 6-7 (2-7) 7-6 (7-1).
Japanese 28-year-old Nishikori did not face a single break point as he defeated home crowd favourite Mannarino in one hour and 27 minutes to progress.
The 10th seed broke the Frenchman at 5-5 in the first set and 3-3 in the second to set up the win.
He will meet seventh seed Kevin Anderson or Georgian Nikoloz Basilashvili in the next round.
On Court One, Isner’s powerful serving ensured he was not broken at all – hitting 33 aces – but wasted opportunities meant he struggled to break Kazakh Kukushkin as the match went on.
The American’s serve only let him down at the second-set tie-break, as the world number 54 forced a deciding set.
That went the distance too but this was a different story for Isner, who won early points against the Kazakh’s serve to take the match.
Isner needs to reach the semi-finals in Paris to have any hope of moving up to ninth in the rankings, which would give him a chance of making the season-ending ATP Finals in London in November.
Later on Wednesday, Alexander Zverev beat Frenchman Frances Tiafoe 6-4 6-4.
The pair traded missed break points in first set before the German, 21, won the final game on Tiafoe’s serve.
In the second set, Zverev broke three times but was broken twice as he wrapped up the eventful match in one hour and 44 minutes.
Ninth seed Grigor Dimitrov is also through after beating Roberto Bautista Agut 7-6 (12-10) 6-4.
Source BBC News