The 17-year-old announced himself to the world when he came off the bench against Aston Villa to score a 93rd minute winner for United in 2009.
But Macheda never reached his potential at Old Trafford, and after six separate loan spells he left the club on a permanent basis in 2014.
The current Panathinaikos forward told Goal: "I don't regret anything.
"Manchester United was a very beautiful experience for me and I still have many fantastic memories of my time there.
"Memories that I still take with me everywhere I go. In Manchester I grew up not only as a player but also as a man and I will always cherish those wonderful memories of my time playing for the biggest club in the world."