1. Giving Paul Pogba up for nothing
Not exactly a transfer mistake as it was out of Alex Ferguson’s control, though if he had just given the Juventus midfielder a chance at Old Trafford he would probably still be there. The France international famously said that he decided to leave when Ferguson decided to play Fabio in central midfield when Scholes was injured over him. Yes, a young incapable wing-back at the heart of midfield, good one Ferguson.