Diego Forlan (Cerezo Osaka)
Despite taking 27 games to score his first goal for the side, Forlan has become a cult hero amongst the United faithful since his departure in 2004. Probably for those ridiculous cornrows.
Subsequent spells at Villarreal and Atletico Madrid, as well as his stunning performances for Uruguay show what a unique talent he can be and could have been for the Red Devils.
Granted, United at the time had Rooney and Ronaldo available in the South American’s position.