Eugenie Bouchard literally has been knocked out of the U.S. Open, the victim of a concussion suffered in a locker- room spill late Friday night.

Just hours before she was to play Italy's Roberta Vinci in a fourth-round match late Sunday, Bouchard, the top-ranked Canadian woman, made official her exit from singles play. She already had withdrawn from scheduled Saturday matches in mixed doubles, partnered with Australia's Nick Kyrgios, and in doubles with Russia's Elena Vesnina.

Bouchard delayed her decision on continuing singles play for a day, but Yahoo Sports Canada reported that her persistent migraine headaches, sensitivity to light, sore neck and dizziness forced her to cancel two attempts to practice early Sunday.

U.S. OpenU.S. Open: Women's results

Bouchard's representatives said she had slipped in a dark training room on her way to an ice bath after her Friday singles match, striking her head and elbow.

At the time of her accident, Bouchard was the only player still alive in all three events -- singles, mixed and doubles -- and was making headway in her struggles to recover her breakthrough major-tournament successes of last year.

Only 20 in 2014, she advanced to the Australian semifinals, French Open semis and Wimbledon final before reaching the fourth round at the U.S. Open. But her 2015 match record is a fairly meek 12-17. After a quarterfinal loss in Australia, she was beaten in the first round at the French and Wimbledon.

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A summer abdominal strain added to her problems, but she came to New York with a surprising new consultant, old champ Jimmy Connors, and talked of revived confidence and a better feel for handling expectations.

"The fact that he truly believes in me," Bouchard said of Connors early in the tournament, "reminded me that, 'Hey, I need to believe in myself as well.' ''

She had tumbled from a 2014 year-end ranking of No. 7 down to 25th, but her Friday victory over Slovakia's Dominika Cibulkova, who had upset No. 7 Ana Ivanovic in the first round, positioned Bouchard as the favorite against No. 43 Vinci to reach the quarterfinals here.