CINCINNATI, OH, USA - Serena Williams has withdrawn from the Western & Southern Open with a back injury.

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Williams, a two-time Western & Southern Open champion, retired during the Rogers Cup final Sunday in Toronto against Bianca Andreescu with the same injury. 

“I am so sad to withdraw from the Western & Southern Open as it is truly one of the tournaments I most love to play," Williams said. "I came to Mason on Sunday and have tried everything to be ready to play tonight, and was still hopeful after my practice this morning. But unfortunately my back is still not right and I know I should not take to the court.

"I really want to thank tournament director Andre Silva and the WTA for giving me every chance to play, and I also want to thank all the amazing fans here in the Cincinnati area for their support – it means so much. I promise I’ll do my best to be back here next year.”

Tuesday’s schedule will now feature lucky loser Jessica Pegula taking on Zarina Diyas in the second night match. Pegula won her first WTA title two weeks ago at the Citi Open.