5) Jose Mourinho
If Manchester United want to bring in a title against the likes Pep Guardiola and Jurgen Klopp, there is only one man they should sign. Jose Mourinho brings with him a guarantee of success even if it is only in the short term. He stays at a club for three years, wins the league, maybe the Champions League and leaves the club in turmoil.
Mourinho has brought stupendous success at each of the clubs he has managed although he has not lasted more than three years at any of them. He comes with a short-term focus on winning titles and not necessarily team building.
The Louis van Gaal reign has been characterised by boring football and some poor results although his focus on youth development must be lauded. If winning the Premier league title is the aim, Jose Mourinho will win it for the Red Devils.