Ronaldo said he is close to his best after making his first competitive appearance in over six months in AC Milan's 2-1 win at Cagliari on Sunday.
The Brazilian, 31, missed the end of last term with a hamstring problem and then injured his leg again in pre-season. Milan kept delaying his comeback and the club's medical staff later admitted misdiagnosing the strain.
He hit a post in Cagliari during a solid display and also won a soft penalty which Kaka missed.
"I'm doing things slowly but I'm not too far from my best form. I had two chances where I've been close to scoring a goal," he told Sky television.
Ronaldo has gained weight in recent years with Milan saying in August that his problem was down to hypothyroidism. He has slimmed down slightly and wants to show Milan he can still be as devastating as he was several years ago.
"We'll see how well I do this year then we can see about a new contract," he added.
Ronaldo was Cup-tied for Milan's Champions League triumph last season following his January move from Real Madrid but hopes to be involved in Wednesday's Group D trip to Benfica where the holders can qualify for the last 16 with a victory.
Coach Carlo Ancelotti knew Ronaldo is ready to return.
"He won a penalty and hit the post. He is in line with what we expected," he said.
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