After signing for Brazilian club Corinthians in December, it was expected Ronaldo would be ready to get back on the pitch within a couple of months, around a year after his career-threatening knee injury with Milan.
However, the two-time Ballon d'Or winner admitted he is not quite fit enough to play competitive football again.
"I don't know when I will be back on the pitch," he told Globo Esporte. "My left leg is not yet strong enough for me to be able to play. A test showed that between the muscle in my right leg and the one in my left leg there is a 30% difference, which is considerable, so it's a risk for me to play. I have to wait until both my legs have the same strength."
The 32-year-old did not want to set a date for his return.
"I ask both my fans and Corinthians to be patient," he continued. "It's not yet the right time for me to play."
The Brazilian star tore a ligament in his left knee on 13 January 2008 during the match Milan-Livorno. Two months ago he signed a one-year contract with the club from Sao Paulo.