Former world No 1 similarly withdrew from the tournament in Toronto with an arm injury.
Maria Sharapova withdraws from Cincinnati as 'precaution' for US Open
Five-time grand slam champion Maria Sharapova has withdrawn from next week's WTA tournament in Cincinnati with a left forearm injury.
The move came a week after the former world No 1 from Russia withdrew from a WTA event in Toronto from the injury she suffered in a second-round match at Stanford, where she withdrew after her opening-round victory.
Sharapova, the 2011 Cincinnati champion, arrived on Friday and made the decision to withdraw after consulting with the event medical staff on Saturday.
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"I arrived in Cincinnati yesterday eager to play. However, following the doctor's advice on-site, as a precaution for the US Open, I am unfortunately withdrawing from the tournament with the left forearm injury I sustained in Stanford," Sharapova said.
"I want to thank the tournament for the wildcard opportunity and really look forward to competing here next year."
Sharapova was due to play French Open champion Jelena Ostapenko in the opening round. Either a qualifier or lucky loser will replace her in the draw.
The injury cast more doubt over Sharapova's participation at the US Open, which starts in New York on August 28. Due to her low ranking, Sharapova would need a wild card to play in the main draw of the tournament.
Sharapova suffered the injury while playing in her first US match in more than two years, defeating American Jennifer Brady 6-1, 4-6, 6-0 in her Stanford opener.
She had not played in the US since March of 2015 due in part to a 15-month doping suspension for the use of meldonium.
* Agence France-Presse