The shocking turn of events broke Osaka into tears as she admitted that she was in pain even before the match.
Venus Williams will join her sister Serena Williams, who also received a wildcard entry in the tournament.
The American leads a star-studded entry list for the National Bank Open, which is scheduled to kick off on August 8.
Daniil Medvedev and Stefanos Tsitsipas survived three-set scares in Toronto as Rafael Nadal withdrew citing injury.
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