The 21-year-old believes he suffered from the weight of expectations at Old Trafford and wishes to remain elsewhere, but he has not ruled out a return to the club in the future.
The Italian burst on to the scene as an unknown teenager against Aston Villa and Sunderland in April 2009, scoring vital goals to help spur Sir Alex Ferguson's side on to the league title.
Macheda has since endured a succession of unsuccessful loan spells in an effort to rediscover form and fitness, most recently landing in Germany with Stuttgart in January, and he has made it clear he wants to depart Old Trafford on a permanent basis in order to continue his progress.
"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," Macheda told the Daily Mail. "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.
"I was only 17 when I made my debut, though, and when I scored those goals people expected me to become the new Wayne Rooney; the next big thing. How could I when I wasn’t even playing every game?
"So that bit was not easy to cope with. When I look back, though, I am still happy about it. It was a fairytale.
"After Manchester it has been a struggle. I have had injuries and loan spells and they haven’t really worked.
"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."