Trezeguet, 31, is out of action until the start of next month with a knee injury sustained in September.
But Antonio Caliendo claims that is not putting off City, who have been linked with a host of players in the January transfer window.
"A man close to Manchester City called me some days ago to tell me of his interest in David," Caliendo told L'Equipe.
"I believe the club are ready to put on the table a bid of more than 20 million euros to get him.
"Manchester City's interest isn't new. It happened last year."
However, Caliendo insists his client is not for sale.
"A big Spanish club also contacted me a few weeks ago, before City did, as well as two clubs from the Persian Gulf," he added.
"But David is untransferable and it is out of the question that I will talk more to these clubs since David still isn't playing again.
"He will stay at Juve through this transfer window."