Carlos Alcaraz withdrew Tuesday from the Cincinnati Open because of a lingering right wrist injury that has sidelined him since April.
The No. 2-ranked Spaniard was hoping to return to defend his title in the hard-court tournament, which serves as an important warmup for the U.S. Open.
"We know Carlos is doing everything he can to get back to playing tournaments as soon as possible," tournament director Bob Moran said in a statement. "We wish him the best with his recovery and look forward to welcoming him back to Cincinnati in the future."
Alcaraz last played at the Barcelona Open, then missed the French Open and the entire grass-court season, including Wimbledon.
He is entered in the U.S. Open, where he is the defending champion. Recent photos and videos on social media have shown the seven-time Grand Slam winner on the practice courts, so it was thought he would be ready to play in the Cincinnati event that begins Aug. 11.