4) Sir Alex letting Paul Pogba leave
Manchester United brought Paul Pogba back to the club for a whopping 120 million making him the most expensive player in the world. However, it is surprising that the club let Pogba leave the club in the first place. Sir Alex’s decision to let go of Pogba is considered as one of the few mistakes the Scott made during his illustrious career. Sir Alex famously fell out with Mino Raiola, Pogba’s agent, during the contract negotiations. He let the Frenchman leave for a pittance. Pogba went on to establish himself as one of the best midfielders of this generation during his time at Juventus, which prompted Jose to bring him back to the club.