The Italian striker was back at Cantley Park, Rovers' training base, on Wednesday to agree a deal to remain with Paul Dickov's Sky Bet Championship side until the end of December.
He is now likely to go straight into the starting line-up when Doncaster resume league action at home to Yeovil on Friday night, live on Sky Sports 1 HD.
"A lot of credit has to go to him," said Dickov. "Because of how he performed in his previous spell with us there were a lot of clubs wanting to take him. He had his choice of six, seven, eight clubs to go to.
"But he's kept his word and come back here. It's given everyone a massive boost.
"Clubs have been sniffing around even when he's been injured. Although it's not that that's caused a bit of a hold-up. Ourselves and United wanted to make sure he was 100 per cent before he came back. We didn't want there to be any doubts about his fitness.
"He trained with us on Wednesday and today (Thursday) and he was flying."
Macheda scored three goals in five Championship appearances, including four starts, for Doncaster before a hamstring injury forced him to return to the Premier League champions.
The 22-year-old marked his first start with both goals in a 2-2 home draw with Nottingham Forest and scored the winner at Hillsborough in a 1-0 derby victory over Sheffield Wednesday.