Rafael Nadal withdrew from the upcoming Monte Carlo Masters on Thursday, saying his body is not yet ready for competition.
Nadal, who has said he expects to retire after the 2024 season, returned to competition in Brisbane in January after almost a year sidelined with a hip flexor injury, but has not played an ATP event since.
"These are very difficult moments for me, sporting wise," Nadal said in a statement on social media. "Unfortunately I have to tell you that I am not going to be playing in Monte Carlo. My body simply won't allow me.
"And even if I am working hard and making the maximum effort every day with all the will to play and compete again at tournaments that have been very important for me, the truth is that I can't play today.
"You have no idea how hard this is for me to not be able to play these events."
The Monte Carlo Masters begins Sunday.
Nadal, 37, has won the event a record 11 times, with his last victory coming in 2018. The 22-time Grand Slam winner also withdrew from last month's BNP Paribas Open at Indian Wells.
Reuters contributed to this report.