“I am very sorry to announce that I won’t be playing in Cincinnati this year,” Nadal wrote on Twitter late on Sunday.
“No other reason than personally taking care of my body and trying to keep as healthy as I feel now.
“I am very thankful to my friend Andre Silva, Tournament Director of the Cincinnati tournament, who after speaking to him on the phone understood what I said and understands the situation.”
Nadal’s withdrawal leaves world number two Roger Federer, who skipped the Toronto event, as the highest seed in Cincinnati.
The US Open starts on Aug. 27 in New York.