The former world No 1's decision comes after she suffered the biggest defeat of her career in San Jose to Johanna Konta
Serena Williams misses Rogers Cup because of 'personal reasons'
Serena Williams has pulled out of next week's Rogers Cup in Montreal for "personal reasons", tournament organisers have announced.
The Wimbledon runner-up suffered the worst defeat of her professional career in San Jose earlier this week when she won just a single game against Johanna Konta.
Speaking after the match, Williams said: "I know I can play a zillion times better, but I have so many things on my mind, I don't have time to be shocked."
Rogers Cup tournament director Eugene Lapierre said in a statement: "Of course, we are disappointed that Serena will not be joining us. Fans were very much looking forward to seeing her in action.
"But, beyond the disappointment, the tournament as a whole remains a high-level competition. The entire top 10 is here, along with 22 of the top 25. There are exciting matches in store from the outset."
Williams is replaced in the main draw by Germany's Tatjana Maria, who will take on Alize Cornet of France in round one.
If Williams had beaten Cornet she would have faced Angelique Kerber, the woman who beat her in the Wimbledon final in July.