PARIS, Nov 4 (Reuters) - Frenchman Gael Monfils withdrew hours before his match against Novak Djokovic in the Paris Masters on Thursday due to an adductor strain, sending the Serbian world number one into the quarter-finals. After his second round win over compatriot Adrian Mannarino, Monfils said he got injured during the match and an ultrasound on Thursday revealed a muscular lesion. "I have the impression that to be optimistic, in about 10 days I will be at 100%, but because of muscular lesion, you just need rest," Monfils told reporters, confirming that it was the end to his 2021 season. Djokovic, who is playing his first tournament since finishing runner-up in the U.S. Open, will face the winner of Cameron Norrie and Taylor Fritz in the quarter-finals. Poland"s Hubert Hurkacz also booked his place in the quarter-finals with a 4-6 7-5 6-2 win over German Dominik Koepfer, to improve his chances of qualifying for the Nov. 14-21 ATP Finals in Turin. The season-ending tournament is played between the top eight men"s singles players and doubles teams. Djokovic, Stefanos Tsitsipas, U.S. Open champion Daniil Medvedev, Alexander Zverev, Andrey Rublev and Matteo Berrettini have qualified for the event with two spots yet to be confirmed. Norway"s Casper Ruud is in seventh place while Hurkacz currently sits in the final automatic qualification spot.