Serena Williams has withdrawn from next week's Rogers Cup in Montreal, citing shoulder inflammation.
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The world No. 1, a three-time winner of the event, announced the news Sunday — 24 hours before the tournament's opening day.
"Due to inflammation in my shoulder, I unfortunately must withdraw from the Rogers Cup," Williams said in a statement reported by the WTA Tour website. "I was looking forward to competing in Montreal and I look forward to returning soon."
Tournament director Eugene Lapierre said the decision was understandable with the Olympic Games in Rio just two weeks away.