#4 Paul Pogba
Quite possibly one of Sir Alex’s biggest mistakes, Paul Pogba left the Red Devils for Juventus on a free transfer. The player left after clashing with the manager over his role in the squad. Pogba believed that he was good enough to play for the senior team, whereas Sir Alex was apprehensive about the same.
The Frenchman was also accused of being disrespectful and the entire saga was bitter from the start to the end.
(Video Courtesy: rom7ooo YouTube Channel)
The midfielder answered back in style as he put in some sizzling performances for Juventus. In the 4 seasons that he spent at the Italian club, Pogba quickly became one of the best young players in the world.
His talent was so enormous and the room for further improvement so high that the Red Devils ended up buying him back for a mammoth price of £89.3 million.