Sinner withdraws from Italian Open with hip injury
Italian Sinner was a doubt for the Rome event which starts on Wednesday and is the last big tournament before the Grand Slam French Open.
"After speaking again with the doctors and specialists about my hip problems I have to announce that unfortunately I will not be able to play in Rome," the world number two said on X, formerly Twitter.
"I'm very sad that I wasn't able to recover as it is one of my favourite tournaments."
The 22-year-old would have been one of the favourites for the Masters 1000 tournament in the Italian capital after winning the Australian Open, his first Slam title, at the start of the year and following that up and his second Masters 1000 crown in Miami in March.
Sinner, who holds a 28-2 record on the season, was due to face Felix Auger-Aliassime in the Madrid quarter-finals on Thursday but revealed he had been battling through a hip issue in the Spanish capital.
Sinner joins world number three Carlos Alcaraz in withdrawing from the clay-court event in Rome after the Spaniard succumbed to a right forearm injury that sidelined him in Monte Carlo and Barcelona.
The pair will now try to recover in time for an assault on the French Open, the season's second major, which starts in Paris on May 26.