American Madison Keys has upset world No.1 Iga Swiatek 6-3 6-4 to reach the Cincinnati Masters quarter-finals.
Swiatek, a two-time grand slam champion, hasn't got past the round of 16 in four tournaments since winning Roland Garros in June.
Thursday's win was the 24th-ranked Keys' first in six matches against a top-ranked opponent. She had never won a set against a No.1.
After dropping the first set and losing the first five games of the second, the Pole Swiatek rallied to win four straight, fighting off one match point before Keys clinched with a forehand winner to the ad court off a shot that clipped the net.
Swiatek won her first two matches against Keys, including 6-1 6-0 earlier this year at Indian Wells.
"She beat me pretty badly the last time we played, so I was happy to get the win," said Keys in an on-court interview.
Two-time Wimbledon champion Petra Kvitova also advanced to the quarter-finals with a 6-1 4-6 6-0 win over Wimbledon finalist, fifth seed Ons Jabeur.
Australian Associated Press
