Rybakina had been due to face Sara Sorribes Tormo of Spain in the third round in the opening match on Court Philippe Chatrier.

"I was not feeling good yesterday and the day before. I didn't sleep last night," said the 23-year-old Wimbledon champion.

"I had fever and a headache and it's difficult to breathe. I tried to play in the warm-up but I feel it's the right decision to withdraw."

Rybakina had swept into the last 32 without dropping a set and had been seeded to face two-time champion Swiatek in the semi-finals.

The Russian-born Kazakh was seen as a potential champion having arrived at Roland Garros with the prestigious Italian Open clay court title under her belt.

"I guess with my allergy that my immune system just went down and I picked up something," said Rybakina. "The doctor said there's a virus in Paris."

Rybakina said she will focus on recovery ahead of defending her title at Wimbledon which gets underway on July 3.

Sorribes Tormo, ranked 132 in the world, will be playing in the second week of a Grand Slam for the first time. She will face either Ekaterina Alexandrova of Russia or Brazil's Beatriz Haddad Maia for a place in the quarter-finals.

Later Saturday, world number one Swiatek takes on China's 80th-ranked Wang Xinyu for a place in the last 16 as she continues her bid to become the first back-to-back champion since Justine Henin in 2007.

World number four Ruud, the runner-up to Rafael Nadal in 2022, dropped the first set before easing to a 4-6, 6-4, 6-1, 6-4 win world number 71 Zhang.

The 26-year-old Zhang was bidding to become the first Chinese man since 1936 to reach the fourth round in Paris.

"It was very tough in the first set, he was hitting many winners and I couldn't find a hole in his game," said Ruud.

"At 5-4 in the second set, he played some sloppy shots and that gave me the set, maybe the match," said Ruud who hit 36 winners and saved seven of 10 break points.

Ruud, playing in the third round for a fifth successive year, will face either Nicolas Jarry of Chile or Marcos Giron for a place in the quarter-finals.

Russian 16-year-old Mirra Andreeva, the breakout star of Roland Garros, faces 2022 runner-up and sixth-ranked Coco Gauff for a place in the fourth round.

Andreeva came through qualifying and has made a mockery of her world ranking of 143 by dropping just six games in two rounds in the main draw.

The France-based Russian is the youngest player to make the last 32 since a 15-year-old Sesil Karatantcheva went to the 2005 quarter-finals.

She is just the seventh player under the age of 17 to make the third round in 30 years, a group that includes the likes of serial Slam champions Serena Williams and Martina Hingis.

"My dream? I know that Novak Djokovic did 22 Grand Slams so I want to go until 25," said Andreeva who played the junior tournament in Paris last year.

Holger Rune, who reached the quarter-finals on his debut in 2022, takes on Argentina's Genaro Alberto Olivieri.

The 231st-ranked Argentine has dedicated his run to the third round to his father who passed away during pandemic.

"He was my sidekick, the person who helped me in every way -- psychologically, emotionally," said the 24-year-old.

"I always remember him. I hope he is now watching everything that is happening to me this week and that he has an even bigger smile than I do."

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