The Italian, who has not made a Premier League appearance for the Red Devils this term, is poised to join the Spanish second-tier outfit until the end of the season
The Spanish club's president Jose Sepulchre revealed that a deal has already been set between the clubs, although the player is yet to agree to the move.
"The agreement between the three parties is complete,” Sepulchre told Efe. “But we still cannot say that the player will come because nothing has been signed yet."
The Italian has seen his first-team opportunities limited by the likes of Robin van Persie, Wayne Rooney, Danny Welbeck and Chicharito.
He has failed to make a single appearance in the Premier League so far this term, featuring twice in the Champions League and once in the Capital One Cup against Chelsea.
Macheda spent the second half of the 2010-11 season with Sampdoria, as they were relegated from Serie A and had a short-lived, and largely unsuccessful, period with QPR last term.