Novak Djokovic said he needed to turn on his “young genes” to recover for Monday's French Open fourth-round match against Francisco Cerundolo.
The world number one won a five-set epic against Italy's Lorenzo Musetti, which finished at 3:07pm local time on Sunday.
It was the slowest finish in clay-court Grand Slam history.
The match did not get underway until 10:37 p.m. Saturday after organizers rescheduled the match at Court Philippe Chatrier to deal with rain delays.
Djokovic won in four hours, 29 minutes and will now try to defend his title against 23rd-seeded Argentine Cernudolo, who has never reached the quarterfinals of a major tournament.
The pair are due to play the third match on the main show court at Roland Garros (not before 15:00 BST).
“If it's the last match of the tournament, it's beautiful to win a match at 3:30 in the morning,” Djokovic said.
“But that's not the case, so we have to try to activate all the young genes and get them back as quickly as possible.”
Sabalenka and Rybakina face toughest test yet
Elena Rybakina, the fourth seed in the women's singles, will face Elina Svitolina at 10am BST at Chatrier.
Next up will be a match between Australian Open champion Aryna Sabalenka and American Emma Navarro.
Second-seeded Sabalenka and Kazakhstan's Rybakina have both won their tournaments without dropping a set so far.
But the pair, seen as the biggest challengers to favourite and two-time champion Iga Swiatek, will face a tougher test on Monday.
Svitolina, the 15th seed from Ukraine, boasts a 2-1 record against Rybakina, while Navarro, the 22nd seed, beat Sabalenka in their first meeting at Indian Wells earlier this year.
Italy's 12th seed Jasmine Paolini and Russia's Elina Avanesyan will open the day on Court Suzanne Lenglen.
Russian teenager Mila Andreyeva and French prospect Varvara Gracheva will compete for the final quarter-final spot.
Elsewhere in the men's singles, Alexander Zverev and 13th seed Holger Run are scheduled to take part in the night session at the Chatrier (before 7.15pm BST).
Germany's Zverev avoided a shock defeat on Sunday by winning a tense five-set match against 26th seed Taron Griekspoor of the Netherlands.
Fifth seed Daniil Medvedev of Russia will face Australia's Alex de Minaur, while two-time finalist Casper Ruud continues his quest for his first Grand Slam title when he takes on 12th seed Taylor Fritz of the United States.
In doubles on Monday, Britain's Joe Salisbury and his American partner, third-seeded Rajeev Ram, will face France's Lucas Pouille and Grégoire Barrere in the third round of the men's doubles.
The pair will first play on Court Simonne Mathieu before Salisbury returns to the same court to face Heather Watson for the second round of mixed doubles.
The British pair will face fourth seeds Neal Skupski and Desiree Krafcik of the United States.
Henry Patten will also be competing in the third round of the men's doubles on Day 9, facing Belgium's Goran Vliegen and Sander Gille and partner Harri Heliovaara of Finland.
