Paris: 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.
Kenin overcomes Ferro
Fourth seed Sofia Kenin recovered from a set down against France's Fiona Ferro at Roland Garros to secure a spot in the quarter-finals on Monday.
Australian Open champion Kenin dropped six games in a row as 49th-ranked Ferro threatened an upset, but the American fought back to advance 2-6, 6-2, 6-1.
Kenin, who defeated Serena Williams in the fourth round last year, will await the winner between Tunisian 30th seed Ons Jabeur and Danielle Collins, whose match was rescheduled to Tuesday due to rain.
"I feel like I'm playing well at the Slams," Kenin, who has made the last 16 or better at the three Majors this season, was quoted as saying earlier.
"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."
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 faces 57th-ranked American Collins, who stunned 2016 champion and 11th seed Garbine Muguruza in three sets.