Novak Djokovic begins the defence of his French Open title at Roland Garros on Tuesday, confident his Grand Slam pedigree will help turn around his lacklustre season as tournament chiefs battled a frustrating five-hour rain delay.

By late afternoon on the third day, only four of the scheduled 40 first-round ties had been completed.

Two-time runner-up Casper Ruud and former Wimbledon champion Elena Rybakina were safely back in the locker room having benefitted from playing under the roofs of the Philippe Chatrier and Suzanne Lenglen courts.

World number one Djokovic, seeking a fourth Roland Garros title and record-extending 25th major, is enduring his worst run since 2018.

Djokovic, 37, has not won a title in 2024 and has yet to make a final with semi-final spots at the Australian Open and Monte Carlo Masters his best performances.

He also suffered the indignity of being accidentally hit on the head by a metal water bottle in Rome which caused nausea and dizziness.

In Geneva last week, where he was knocked out by Tomas Machac of the Czech Republic, Djokovic said he had been suffering from a stomach problem.

"They are rather bumps on the road," said Djokovic, who watched his long-time rival and 14-time champion Rafael Nadal bow out of the tournament against Alexander Zverev on Monday.

When asked to elaborate further on his difficulties so far this season, Djokovic opted for discretion.

"Various things have been happening in the last couple of months, but I don't want to get into it. I don't want to open Pandora's Box."

On Tuesday, Djokovic will take on French wildcard Pierre-Hugues Herbert, the world number 142 who hasn't won a match on the main tour this year.

Ruud, who won clay-court titles in Barcelona and Geneva in the build-up to Roland Garros, cruised to a 6-3, 6-4, 6-3 victory over Brazilian qualifier Felipe Meligeni Alves.

"It's great to be back here at Roland Garros," he said. "Hopefully I can make it another good year here."

Ruud was beaten in straight sets by Novak Djokovic in last year's final following a one-sided loss to Rafael Nadal in the 2022 showpiece.

He also lost the 2022 US Open final to Carlos Alcaraz.

Frenchwoman Alize Cornet's career ended with a straight-sets defeat by Zheng Qinwen in her record-extending 69th consecutive Grand Slam appearance.

Cornet was no match for China's Australian Open runner-up Zheng, losing 6-2, 6-1.

She made her debut at Roland Garros as a 15-year-old in 2005 and has not missed a Grand Slam tournament since the 2006 US Open.

- 'Cried watching Rafa' -

Cornet reached a career-high ranking of 11th in 2009 and enjoyed a surprise run to the 2022 Australian Open quarter-finals.

"I already cried yesterday watching Rafa," said a tearful Cornet after seeing Nadal lose what was likely his last match at the French Open on Monday.

Over on Court Suzanne Lenglen, Rybakina powered into the second round with a 6-2, 6-3 victory over Belgian Greet Minnen and could face three-time Grand Slam champion Angelique Kerber for a place in the last 32.

Kazakh world number four Rybakina is the only player to defeat tournament favourite Iga Swiatek on clay this season, in the Stuttgart semi-finals in April.

Elsewhere on Tuesday, two-time Australian Open champion Aryna Sabalenka gets her bid to reach a first Roland Garros final underway.

The world number two has reached at least the semi-finals in each of the past six Grand Slam events.

Sabalenka is also the only woman to beat world number one and three-time French Open winner Swiatek in a final on clay -- in Madrid last year -- since the Pole lost her first WTA title decider as a teenager in 2019 at a low-key event in Switzerland.

The 26-year-old Sabalenka had never even reached the second week at Roland Garros until last year, when she was knocked out by Karolina Muchova in the semi-finals.

She starts her Paris campaign against Russia's Erika Andreeva.

Also on court in the men's singles is Argentine qualifier Roman Andres Burruchaga who has sporting success in the blood.

His father Jorge famously scored the winning goal for Diego Maradona's Argentina in the 1986 World Cup final against West Germany.

Ranked at 144, the 22-year-old is making his Grand Slam debut and takes on Germany's Jan-Lennard Struff.