Serena Williams will be missing from Montreal next week.
The 23-time Grand Slam champion withdrew from next week's Rogers Cup citing "personal reasons."
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"We are disappointed Serena will not be joining us," tournament director Eugene Lapierre said. "Fans were very much looking forward to seeing her in action."
Williams' departure gives German Tatjana Maria a wild card into the main draw.
The withdrawal comes after Williams suffered the worst loss of her career in San Jose opener as Johanna Konta reeled off 12 consecutive games in a 6-1, 6-0, demolition of the former world No. 1.
The tournament tweeted news of Williams' withdrawal.
The Wimbledon finalist faced a tricky draw in Montreal.
Williams was scheduled to open against Alizé Cornet, who has scored three career wins over the former No. 1, with a second-round clash looming vs. Wimbledon champion Angelique Kerber.
Maria will now face Cornet in the opening round.
"Beyond the disappointment, the tournament as a whole remains a high-level competition," Lapierre said. "The entire top 10 is here along with 22 of the top 25."