5) Jose Mourinho letting Kevin De Bruyne go
The Portuguese is unarguably one of the greatest managers of all time. He is known for his obstinate attitude and is a well-known pragmatist. However, the self-proclaimed Special One got it horribly wrong when he decided to let of Kevin De Bruyne. Mourinho excoriated De Bruyne for his lack of commitment and did not hesitate selling the talented Belgian. De Bruyne has since went on to prove Jose’s decision to denigrate him as the wrong one. He is now a prominent figure under Pep Guardiola and is easily one of the best players in the premier league at the moment.