Italian fourth seed Jannik Sinner has withdrawn from the Paris Masters with fatigue.
Sinner beat American Mackenzie McDonald in the second round but did not start play until after midnight and finished at 02:37 local time on Thursday.
The 22-year-old was scheduled to play Australian Alex de Minaur in the third round later on Thursday.
Meanwhile, world number one Novak Djokovic laboured to a 4-6 7-6 (7-2) 6-4 win over Dutchman Tallon Griekspoor.
The Serb looked out of sorts and had to come from behind to grind out the victory but will face Danish sixth seed Holger Rune in the quarter-final.
In the early hours of Thursday morning, Wimbledon semi-finalist Sinner had battled back from losing a first-set tie-break to beat McDonald 6-7 (6-8) 7-5 6-1 but could not face the prospect of playing again just 14 hours later.
"I am sorry to announce that I am withdrawing from today's match in Bercy," said Sinner on X.
"I finished the match when it was almost three in the morning and didn't go to bed until a few hours later. I had less than 12 hours to rest and prepare for the next game.
"I have to make the right decision for my health and my body."
On Tuesday, Dominic Thiem beat Stan Wawrinka at 02:22 local time, in what has become a far from unusual finishing time in tennis.
'He should not have had to choose'
Russell Fuller, BBC Sport analysis
Sinner says he pulled out to prioritise his health and body - and points out that after completing his post-match routine in the early hours of this morning, he had less than 12 hours to rest and prepare for today's match.
He has two very important tournaments still to play. The ATP Finals on home soil in Turin in 10 days' time, followed by the Davis Cup Finals in Malaga with a promising Italian team.
But he should not have had to choose.
Both the ATP and the WTA Tour are currently looking into what they can do to control the recent trend of ludicrously late finishes, but it is not easy for them to dictate to tournament owners and promoters.
Some tournaments have reduced the number of matches on the show courts, but in Paris they still try to shoehorn four singles matches into the 11am day session, and then two more into a night session which frequently gets under way later than the scheduled 19:30 start.
Djokovic survives second-round scare
Djokovic's bid for a record-extending seventh Paris Masters title continues but the 36-year-old's victory over world number 23 Griekspoor was far from straightforward.
The 24-time major champion took a 4-1 lead in the opening set but laboured through the next four games as the Dutchman capitalised on his opponent's struggles to edge ahead then serve out the set.
A lethargic Djokovic called for the doctor before trying to dominate points from the baseline in an effort to limit his movement in the second set, saving break points in the ninth game and forcing a decider with a dominant tie-break win.
Griekspoor will perhaps not get a better opportunity to beat Djokovic, who was in clear discomfort, but let the prospect of what would be the biggest win of his career get away from him.
Djokovic's break in the third set was instantly cancelled out but he seemed spurred on by the crowd's boos after he sarcastically clapped them for favouring his opponent, winning eight consecutive points without reply to secure victory.
Later on Thursday, Rune got the job done quickly against German Daniel Altmaier, winning 6-3 6-3 in one hour and 20 minutes to set up the Djokovic tie.
With Sinner out, De Minaur will face Russian Andrey Rublev in the quarter-final after the fifth seed beat Dutch player Botic van de Zandschulp 6-3 6-3, qualifying for the season-ending ATP Finals in Turin in the process.
Joining him in Italy will be Greek seventh seed Stefanos Tsitsipas, who beat German 10th seed Alexander Zverev 7-6 (7-2) 6-4.
Tsitsipas, who reached the semi-finals in Paris last year, will face Russian 16th seed Karen Khachanov while Grigor Dimitrov comfortably beat Kazakhstan's Alexander Bublik 6-2 6-2 and will meet Poland's Hubert Hurkacz next.