Macheda joined Stuttgart in January on a loan deal until the end of the season, while the Bundesliga club have the option to buy him in the summer.
He has also been linked with a return to boyhood club Lazio, who he left for Old Trafford as a 16-year-old in 2007.
Macheda made an initial impact with United, scoring a memorable late winner against Aston Villa on his senior debut, but struggled to establish himself as a first-team regular.
The 21-year-old Italian is settling into life in Germany and admits it "wouldn't make sense" to go back to United, where he has been sent out on loan three times in the last two years; to Sampdoria and QPR as well as Stuttgart.
The striker, contracted at Old Trafford until next summer, told the Daily Mail: "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.
"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."