2) Andrea Pirlo to Juventus
Letting go of the majestic Andrea Pirlo could well be AC Milan’s biggest mistake ever. After nearly 10 years of service to the reds, Allegri let Pirlo leave the club for free stating that he was too old. However, the club lived to regret its mistake as Pirlo signed for rivals Juventus and went on to reach great heights. Placed in front of the trio of Chiellini,
Bonucci and Barzagli, Pirlo flourished in Antonio Conte’s setup. In his four years in Turin, Pirlo won four Serie A titles and reached the Champions League final.