Five years ago, Danka Kovinic twice came within two points of upsetting Petra Kvitova, but was unable to close the deal. In the third round of the 2021 Volvo Car Open, she made no mistake, ousting the No.3 sed 6-4, 6-1 in one hour and 16 minutes.
There had been a few signs that Kovinic could be a serious threat. She had pushed Kvitova all the way in both their previous meetings, falling 6-3, 4-6 7-6(5) in the first round of Indian Wells 2016 and 6-2, 4-6, 7-5 at the same stage of Roland Garros two months later.
Additionally, Charleston has historically been a happy hunting ground for the Montenegrin. She reached her only previous WTA 500 quarterfinal here in 2015, a run that included defeats of a 17-year-old Naomi Osaka in qualifying and an 18-year-old Belinda Bencic in the second round.
Indeed, Kovinic has only lost to sometime Charleston winners in her three prior main draw appearances: to defending champion Andrea Petkovic in the 2015 quarterfinals, and to eventual titlists Sloane Stephens in the 2016 second round and Daria Kasatkina in the 2017 first round.
Against Kvitova, the World No.91 held her nerve to edge an evenly contested first set, and pulled away in the second as the Czech collapsed into error. Kovinic was unfazed by Kvitova's power, happily engaging in high-octane exchanges and frequently coming out on top of them.
"We both have pretty big serves and she's very good hitting from the baseline," said Kovinic afterwards. "Today it was the key that I tried, and did it really well, to take her pace of the ball and use her energy. As you can see, her returns on my second serve were sometimes incredible - I didn't even move and the ball passed by me, but somehow I managed."
Kovinic also passed the key mental tests of both sets' longest games. After four breaks in the first six games, the opening act was finely poised - but it was Kovinic who saved a break point and survived three deuces to hold for 4-3.
In the second, her first four points to take a 5-1 double-break lead passed her by as Kvitova threatened a comeback. Kovinic held firm, though, as Kvitova ballooned a backhand wide on the fifth. Having failed to serve out their Roland Garros clash in 2016, Kovinic was emphatic this time, sealing her third career Top 20 win with four consecutive unreturned serves.
Danka Kovinic's Top 20 wins
2016 Madrid R1, d. Roberta Vinci 6-4, 6-2
2020 Rome R2, d. Belinda Bencic 6-3, 6-1
2021 Charleston 500 R3, d. Petra Kvitova 6-4, 6-1
Kovinic will next face another unseeded player, Yulia Putintseva, in the quarterfinals. The Kazakh advanced when No.6 seed Garbiñe Muguruza was forced to retire leading 6-0, 2-2 due to a left leg injury.
"I was already feeling some pain in my first match," explained Muguruza afterwards. "The switch of hard courts to clay was tough, and in a very short amount of time. I started very well, and all of a sudden I felt a sharp pain in my leg, and it got worse. I didn't want to continue without playing my best tennis. It didn't make sense to me."
The Spaniard dominated the first set with 10 winners to Putintseva's one, coming forward at every opportunity to hit through her opponent's defence. But after winning the first seven games, she called for the trainer, and lost the next two games as Putintseva began to use the dropshot effectively.
After a medical timeout, Muguruza broke Putintseva back, but after pulling up on a volley and getting pegged back to a fifth deuce in the next game decided to call it quits. It will be scant consolation to the Dubai champion that her first-set performance means that she ties Maria Sakkari for the most bagel sets delivered in 2021 WTA main draws, with five apiece.
Garbiñe Muguruza's 2021 bagel sets
d. Alison Van Uytvanck 6-2, 6-0, Yarra Valley Classic R2
d. Marketa Vondrousova 6-0, 6-1, Yarra Valley Classic SF
d. Margarita Gasparyan 6-4, 6-0, Australian Open R1
d. Iga Swiatek 6-0, 6-4, Dubai R3
l. Yulia Putintseva 6-0, 2-2 ret., Charleston 500 R3
"First of all, she was playing really great tennis since the first point," said Putintseva afterwards. "I tried to fight back, I tried to do my best, and in the second set I could at least make it to be even. But for now I don't feel like I deserve this, to go through. I wish her a speedy recovery - she's having a great season."
Elsewhere, Abu Dhabi finalist Veronika Kudermetova reached her third quarterfinal of the season with a 6-0, 6-3 defeat of qualifier Kurumi Nara. The Russian captured the Nara serve in a titanic first game, taking her fifth break point after nine deuces, but rolled from there on.