World number two Naomi Osaka suffered a surprise third-round defeat to Swiss wildcard Jil Teichmann at the Cincinnati Masters.
The Japanese star, 23, lost 3-6 6-3 6-3 to the world number 76.
“I have high expectations of myself but there was nothing more I could do to win this match,” Osaka said.
Elsewhere, top seeds Daniil Medvedev and Ashleigh Barty are among the big names through to the quarter-finals in Cincinnati.
Russian world number two Medvedev beat Bulgaria’s Grigor Dimitrov 6-3 6-3 in the men’s draw.
He extends his winning streak to seven matches, having won the Canadian Open title on Sunday.
Meanwhile, British duo Andy Murray and Daniel Evans, who both exited the Cincinnati Masters earlier this week, have been given wildcards for the Winston-Salem Open – the final tournament before the start of the US Open on 30 August.
Murray was beaten in the second round by Hubert Hurkacz while British number one Evans lost to 10th seed Diego Schwartzman.
Reigning US and Australian Open champion Osaka, who lost in the third round at the recent Olympics in Tokyo, made 41 unforced errors in the match while hitting only 17 winners.—BBC