Eugenie Bouchard has withdrawn from the US Open due to concussion.
Bouchard, seeded 25th in Flushing Meadows, suffered a head injury after slipping and falling in the locker room following competition on Friday evening.
The 2014 Wimbledon finalist pulled out of the doubles and mixed doubles on Saturday but had delayed her decision regarding the singles, where she was due to meet Italian Roberta Vinci on Sunday in the fourth round.
A tournament statement read: "Eugenie Bouchard is withdrawing from the women's singles competition at the 2015 US Open due to a concussion."
Canada's Bouchard beat Slovakian Dominika Cibulkova in the third round on Friday before teaming up with Australian Nick Kyrgios in the mixed doubles later in the afternoon.
The pair overcame Elina Svitolina and Artem Sitak to reach round two. She had been due to play in the women's doubles with Russian Elena Vesnina on Saturday but in the morning announced her withdrawal.
Bouchard reached the Wimbledon final in 2014, as well as the semi-finals at the Australian and French Open, but she has struggled for form this year.
Her victory over Cibulkova was the first time she has managed three consecutive victories since January.
