#4 Kevin De Bruyne
More than De Bruyne hating Jose Mourinho for his mistreatment at Chelsea, Mourinho will hate himself for having let go off a gem-of-a-player in Belgian sensation KDB.
Their stand-off dates back to the back end of 2013, when Mourinho gave a damning critique of the Genk and Werder Bremen starlet prior to his departure to Wolfsburg. The former Madrid boss refused to grant De Bruyne a starting place in his Chelsea team. Mourinho let go of the Manchester City star and felt he had made a great decision, because, in his words, "If De Bruyne stayed here, not happy and not motivated, and we'd sold him after a year, we'd have got less - 50 per cent less than we sold him for.
When asked why he let go of De Bruyne, the Special one responded saying “With De Bruyne, if you have a player knocking on your door and crying every day he wants to leave, you have to make a decision. He was not ready to compete. He was an upset kid, his training was very bad.”