#1 Massimiliano Allegri

Max Allegri's work at Juventus isn't given the credit it deserves. Working with a squad that is taken apart and rebuilt almost every summer, Allegri manages to keep his team competitive on every front.
Managing the egos of big players is no problem for him, having worked with Dani Alves, Patrice Evra, and now Gonzalo Higuain and Paulo Dybala. Getting the best out of his squad at Juventus has been a bit of a cake walk. Imagine what he could do with a squad like Real Madrid.
Florentino Perez is probably picturing it. Juventus, while still one of the best teams in Europe, do not have the finances to compete with the likes of Man City and PSG. Real do. Allegri will mesh into the club, much the same way Valverde has with Barcelona. His unassuming character means he will just carry on with his work without press battles, and let his team's performances to the talking.
With Allegri looking increasingly likely to leave this summer, the stars could just be aligning in Madrid.