Nadal, a 14-times Roland Garros champion, skipped the ongoing Madrid Open and has also missed tournaments at Indian Wells, Miami, Monte Carlo and Barcelona.
“I’m very sorry to announce that I will not be able to be in Rome,” the 36-year-old Spaniard, a 10-times champion in Rome, said in a statement.
“You all know how much it hurts to miss another one of the tournaments that have marked my professional and personal career for all the love and support of the Italian tifosi.
“Despite having noticed an improvement in recent days, there have been many months without having been able to train at a high level and the readaptation process has its times and I have no choice but to accept them and continue working.”
Nadal, who has dominated the claycourt season for years, has competed at Roland Garros every year since winning the first of his men’s record 22 major titles in Paris in 2005. The French Open begins on May 28.
He was initially set to miss up to eight weeks after suffering the hip flexor injury in January in his second-round match against Mackenzie McDonald that effectively ended his Melbourne Park title defence.
But a setback in his recovery ahead of the Madrid tournament and his subsequent withdrawal from Rome means that if he is fit in time, Nadal would be heading to Roland Garros without having played any competitive matches.
In March, Nadal slipped out of the top 10 of the ATP ranking for the first time since 2005 and is currently ranked 14.