American Madison Keys swept past Wimbledon champion Elena Rybakina 6-2, 6-4 at the Cincinnati Open on Friday, setting up a semifinal clash with Petra Kvitova after the Czech defeated Australian qualifier Ajla Tomljanovic.
Having dispatched world No. 1 Iga Swiatek in the third round, the 27-year-old Keys carried that momentum into the quarterfinals with a dominating win over 25th-ranked Rybakina.
Both Keys and Rybakina had reached the last eight without dropping a set and it would be the American keeping the unblemished record.
"I knew she is a remarkable player and she can turn it around at any moment so I knew I had to try to stay out in front because at any moment she can go on a roll," said Keys, finalist at the 2017 US Open.
"I think that is kind of the key against her. If you back off at all then she gets to dictate and run you around."
One of the WTA Tour's big-hitters, ranking No. 2 on the season ace list, Rybakina struggled with her serve the entire match, hitting just one ace while piling up four double faults.
In the first contest on a muggy Centre Court, Keys, Cincinnati champion in 2019, got out to a flying start breaking Rybakina twice on the way to a 4-0 lead before the Kazakhstan player was finally able to hold serve.
After surrendering the opener Rybakina rallied in the second with an early break to jump out in front 2-0.
But Keys dug in, sweeping the next five games to retake control 5-2 and after a late wobble closed out the contest on her fourth match point when Rybakina hit her return into the net.
Later, twice Wimbledon champion Kvitova reached the last four in Cincinnati for the third time in her career with a business-like 6-2, 6-3 victory over Tomljanovic.
The other semifinal will see the only remaining seed, No. 6. Aryna Sabalenka take on French qualifier Caroline Garcia, who continued her upset run through the draw with 6-1, 7-5 win over seventh-seeded American Jessica Pegula.
Belarusian Sabalenka, who finished last season as the world's No.2-ranked player, advanced with a 6-4, 7-6(1) win over China's Zhang Shuai.
In the men's section, world No. 1 Daniil Medvedev and fourth seed Stefanos Tsitsipas defused big-serving American threats Taylor Fritz and John Isner to reach the semifinals.
Medvedev, champion in Cincinnati in 2019, sharpened his game for his upcoming US Open title defence with a 7-6(1), 6-3 win over 11th seeded Fritz, while Tsitsipas could manage only a single break chance in a three set slugfest with Isner but it was enough to clinch a 7-6(5), 5-7, 6-3 victory.
Medvedev's win was powered by 18 aces while a misfiring Fritz, one of the game's big-hitters, had just three offset by three double-faults.
Isner, the biggest server in men's tennis with nearly 200 more aces than his nearest rival Nick Kyrgios, also had 18 aces but it was still not enough to put away his patient Greek opponent.
British No. 1 Cameron Norrie held off third seed Carlos Alcaraz to claim a 7-6(4), 6-7(4), 6-4 win and book his place in the semifinals, where he will face Borna Coric after the Croatian saw off Felix Auger Aliassime 6-4, 6-4.
