In the third round of the Canadian Open, british no. 1 Katie Boulter fell to Aryna Sabalenka in straight sets.
Although it took an hour and 23 minutes for the second seed from Belarus to win 6-3 6-3, Boulter showed promise ahead of the US Open, which begins in two weeks.
In Toronto, the 28-year-old created four break points against the world’s third-ranked player, but none of them were converted.
Boulter, who advanced to the quarterfinals of the Olympic Games in the women’s doubles division, will compete in the Cincinnati Open the following week as her last preparation match before the US Open.
American top seed Coco Gauff is also out of the Toronto event as she surprisingly lost 6-4 6-1 against Diana Shnaider of Russia.
The defending US Open champion was knocked out in 70 minutes by the world number 66 and acknowledged she struggled physically and mentally.
“Sometimes I question whether I should have played or not,” Gauff said.
“But at the end of the day I wanted to test myself and see how I would do being mentally tired a little bit and physically fatigued.
“I didn’t have high expectations, but I wish I could have competed better, even if it resulted in a loss. I don’t think I competed well.”