Petra Kvitova returned to the French Open quarter-finals for the first time in eight years on Monday while Novak Djokovic continued his bid to become the first man in half a century to win all four Grand Slam titles twice.
Two-time Wimbledon champion Kvitova is through to the last eight at Roland Garros for just the second time. Her best run in Paris came when she reached the semi-finals in 2012.
Seventh seed Kvitova, who missed last year's tournament due to an arm injury, defeated China's Zhang Shuai 6-2, 6-4 and will next play German veteran Laura Siegemund.
"It's been really difficult. It was a tough one for sure," said Kvitova, who will climb back into the top 10 following her performance in Paris.
"She served very well and played very aggressive. I'm really happy I managed to win even if I didn't manage to serve it out at 5-2."
"When the roof is closed it's like being indoors and I really love to play," added Kvitova.
Siegemund, 32, advanced to her first Grand Slam quarter-final in singles after defeating former junior champion Paula Badosa of Spain 7-5, 6-2.
She became the fourth unseeded player to make the last eight this year, joining Iga Swiatek, Nadia Podoroska and Martina Trevisan.
"I didn't get angry when things weren't going my way," said Siegemund, who trailed Badosa 5-3 in the first set.
"I think we were both kind of struggling but I think I kept it together better."
Siegemund won last month's US Open women's doubles titles alongside Vera Zvonareva.
Later on Monday, world No 1 and 2016 French Open champion Djokovic plays 15th seed Karen Khachanov, who claimed his biggest win to date against the Serb in the French capital.
Djokovic is into the Roland Garros last 16 for a record-equalling 11th successive year and is chasing an 18th Grand Slam title.
The Serb has dropped just 15 games in three rounds, improving his record this season to 34 wins against one loss - his US Open disqualification.
Khachanov upset Djokovic in the final of the 2018 Paris Masters and is attempting to reach quarter-finals here for the second time in a row.
"Maybe mentally you know that you beat him in this particular match, for sure it gives you the confidence inside to know that you've done it already once at least," said Khachanov.
"That's the only thing that might help on a mental preparation to be ready for whatever happens," he added.
"The deeper you go the tougher opponents you face. This is what it's all about."
Kenin feeling confident
Only Djokovic has won more titles in 2020 than Andrey Rublev, the Russian 13th seed who plays world number 63 Marton Fucsovics, the first Hungarian man in the second week since Balazs Taroczy in 1984.
Rublev won on clay in Hamburg last week to add to victories at Doha and Adelaide at the start of the campaign.
Greek fifth seed Stefanos Tsitsipas takes on Grigor Dimitrov while German qualifier Daniel Altmaier looks to extend his shock run against US Open semi-finalist Pablo Carreno Busta.
World number 186 Altmaier is just the fourth man in 20 years to reach the round of 16 on his Grand Slam debut.
Only four seeds remain in the women's draw, with No. 4 Kenin the second highest left behind third seed Elina Svitolina following the exit of title favourite Simona Halep.
Australian Open champion Kenin, who defeated Serena Williams in the fourth round last year, will face unseeded French player Fiona Ferro.
"I feel like I'm playing well at the Slams," said Kenin, who has made the last 16 or better at the three majors this season.
"It's not easy, everyone is playing their best tennis at the Grand Slams. But I definitely feel like I should get deep in a tournament."
Ons Jabeur is targeting a second quarter-final in three Slams after becoming the first Arab woman to make the fourth round here.
The Tunisian 30th seed next faces 57th-ranked American Danielle Collins, who stunned 2016 champion and 11th seed Garbine Muguruza in three sets.
French Open results at Roland Garros on Monday, the ninth day of the delayed 2020 championship (x denotes seeded player):
Petra Kvitova (CZE x7) bt Zhang Shuai (CHN) 6-2, 6-4
Laura Siegemund (GER) bt Paula Badosa (ESP) 7-5, 6-2