PARIS: 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 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, playing his first tournament since finishing runner-up in the U.S. Open, will take on American Taylor Fritz in the last eight.

World number two Daniil Medvedev needed three sets to see off Sebastian Korda of the United States 4-6 6-1 6-3.

The U.S. Open champion will play Frenchman Hugo Gaston, who stormed back from a 0-5 second set deficit to beat Spaniard Carlos Alcaraz 6-4 7-5 and reach the quarter-finals.

Norwegian Casper Ruud crushed American Marcos Giron 6-2 6-1 and will meet German Alexander Zverev in the next round after the latter edged Bulgarian Grigor Dimitrov 7-6 6-7 6-3.

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, improving 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, Medvedev, Zverev, Andrey Rublev, Matteo Berrettini and Ruud have qualified for the event with one spot yet to be confirmed.

Hurkacz sits in the final automatic qualification place and can seal his berth with victory over Australian James Duckworth on Friday.