Rafa Nadal has withdrawn from next week's U.S. Open tune-up event in Montreal, Canada due to the same abdominal strain which forced him to miss his Wimbledon semi-final last month, he said on Friday.
World number three Nadal's quest for a calendar Grand Slam ended after he pulled out of his highly anticipated showdown against Australia's Nick Kyrgios less than 24 hours before the match.
The 26-year-old Nadal, who has won 22 major titles, is a five-time champion at the ATP 1000 event in Montreal, which begins on Monday.
"I have been practicing for a while now without serving and started with serves four days ago. Everything has been going well, however yesterday, after my normal practice, I felt a slight bother on my abdominal and today it was still there," Nadal said in a statement.
"After speaking with my doctor we prefer to take things in a conservative way and give a few more days before starting to compete.
"I am very sad not to finally travel to Montreal and to play a tournament that I have won five times and I love to play. I seriously hope I can come back there to play in front of the amazing crowds up there."
Wimbledon champion Novak Djokovic also withdrew from the event on Thursday as he cannot enter the country without being fully vaccinated against COVID-19, while Britain's Andy Murray was handed one of four wildcards.