CINCINNATI (AFP) — Top-ranked Daniil Medvedev advanced to the ATP and WTA Cincinnati Masters quarterfinals on Thursday while women's world No. 1 Iga Swiatek was upset by American Madison Keys.

Top seed Medvedvev kept Denis Shapovalov winless against world heavyweights with a 7-5, 7-5 victory while Poland's Swiatek lost 6-3, 6-4 to 2019 Cincinnati champion Keys, who needed five match points to finish off the shock triumph.

Shapovalov, who lost in an hour and three-quarters, has dropped all eight career matches he has played against the elite echelon.

Medvedev moved into a quarterfinal against 11th seed Taylor Fritz after the American stopped number six seed Andrey Rublev 6-7 (4/7), 6-2, 7-5.

"It was a fight today, definitely not easy," said Medvedev, who clinched the top US Open seeding when Rafael Nadal lost here in the second round.

"The match was pretty tight, played at a great level. My goal was to stay in every point possible and try to put pressure on him if I had the chance."

Medvedev secured late breaks in both sets as he matched his volatile Canadian opponent.

Medvedev and Fritz have never played.

"We trained together at the start of the season before the ATP Cup," Medvedev said.

"He won Indian Wells, he's a Masters champion. I need to be at my best to try and beat him."

Unseeded Keys was thrilled with her defeat of Swiatek, against whom she had lost two prior matches.

"I had a couple of games with a couple of match points," Keys said.

"She beat me pretty badly last time so I'm happy to get the win."

Swiatek never found an ace and was broken five times as she fought back in vain after standing one game from defeat.

It was the second week in a row that the Pole, who put together a 37-match win streak this season, lost in a Masters third round. She suffered the same fate in Toronto seven days earlier.

Keys plays on Friday against Wimbledon winner Elena Rybakina, who advanced to the last eight 6-2, 6-4 over Alison Riske-Amritraj.

Also ousted was Estonian second seed Anett Kontaveit, who fell to China's Zhang Shuai 2-6, 6-4, 6-4.

Czech Petra Kvitova began turning her luck against top-five opponents as she defeated Wimbledon finalist Ons Jabeur 6-1, 4-6, 6-0.

The third-round victory was a duplicate of Kvitova's victory over Jabeur a year ago.

Kvitova, twice a Wimbledon champion, broke six times as her fifth-ranked Tunisian opponent committed six double-faults in the contest.