British number one Katie Boulter was swept aside in straight sets by American teenager Coco Gauff in the second round of the National Bank Open.
Boulter, 27, had not dropped a set in coming through two qualifying matches and her main-draw opener in Montreal.
But she lost 6-2 6-2 to 19-year-old Gauff, who will face Wimbledon champion Marketa Vondrousova or the returning Caroline Wozniacki in the last 16.
Ex-world number one Wozniacki won her first-round comeback match on Tuesday.
Gauff, ranked sixth in the world, made a blistering start against Boulter on Wednesday as she lost just three points in the first four games of the opening set, twice breaking serve to establish a 4-0 lead.