Aleksandra Wozniak has pulled out of the Bell Challenge after injuring her shoulder while warming up for her match against Melanie Oudin.
The Canadian fourth seed entered the second-round clash against the American as favourite on Thursday before the injury led to her withdrawal in Quebec City.
Wozniak was the second-highest seed left at the WTA International tournament after several upsets early in the event.
There was yet another upset on Thursday as seventh seed Petra Martic was sent packing by Georgian Anna Tatishvili.
Croatian Martic put in only 43 percent of first serves, giving Tatishvili too many opportunities as the world No.52 won 6-2 6-3 in one hour and 18 minutes.
Another Croatian, Mirjana Lucic, also tasted defeat with a 6-7 (2-7) 6-2 6-4 loss to Belgian Kirsten Flipkens.
Flipkens, who stunned top-seeded wildcard Dominika Cibulkova in the opening round, served 12 aces in the clash, which lasted two hours and 13 minutes.
Canada's Eugenie Bouchard also departed in the second round, losing 7-6 (7-2) 2-6 7-6 (7-4) to Czech eighth seed Lucie Hradecka.
A wasteful Bouchard served 11 aces but missed her chances in the deciding set, converting just one of seven break-point opportunities.