The Argentina international cited a desire to be closer to his daughters when informing City of his intention to move on during the summer transfer window.
Potential suitors are currently pondering whether to make a move for the Blues skipper and speculation over his future can be expected to continue during his involvement in the Copa America.
Hamann, who played for City between 2006 and 2009, knows the club would find it hard to replace their star striker but he accepts they could well be looking for a new stellar signing.
"He's got a contract so it's not really down to him but if a player doesn't want to be there it makes no sense to keep him," Hamann, who has been unveiled as the new Stockport boss, told Sportinglife.com.
"I'm sure they'll come to the right decision and find the right solution to deal with it but it's now down to Garry Cook, Roberto Mancini and Tevez.
"He'll be hard to replace because he's scored a lot of goals and done great for the club.
"If there's a player out there who can replace him City will make a move and get him."
Source: Team Talk
Source: Team Talk