#4 Harry Maguire
Harry Maguire is an English Footballer. He is currently signed to Leicester playing Centre-Back. Maguire is good enough to sign United or any other club. His techniques to defend the ball is excellent. This could have lead Manchester United to bring some interest in him after seeing his performance.
He has performed extremely well in FIFA 2018 World Cup and considering how Manchester United needs to strengthen their squad's defensive position Maguire would have proven a far better choice than anyone.
Maguire signed to Leicester in July 2017 and his contract will be running till June 2022. And seeing how important this 25-year-old man is to Red Devils than to Foxes, Mourinho should have made a quick move to sign him up when he had the chance.