Macheda concedes his time with United is coming to an end.
"After Manchester it has been a struggle. I have had injuries and loan spells and they haven't really worked," he told the Daily Mail. "But I am adapting now here at Stuttgart. That takes time. The important thing now is to find my place; get some playing time and develop as a player.
"Manchester United was more difficult than any club in the world because of the talent of the players there and because of the attention and the pressure.
"It wouldn't make sense to go back and do what I have done for the last two years. Maybe in the future I could go back, but not now."