#3 Arrigo Sacchi

He is one of the few managers who didn't play football professionally. In this regard, he once famously said: "I did not realize that one had to be a jockey to be a horse." He first managed Parma, where he didn't win many titles but caught the eye of the owner of Milan when Parma defeated Milan in the Coppa Italia.
In AC Milan, he instantly started instituting new forms of training such as visualizing a situation on the field and accordingly demonstrate the movement required for it. The results didn't come instantly but eventually, players responded well to his methods and went on to win the league. Apart from this, Sacchi later went on to win two European championships.
Sacchi's tactics were different from others at that time. He used a traditional 4-4-2, but it was all with many interchanges and nuances. His team played an extremely high offside line, it was a tactic that he used to frustrate the opponents.
Here are some quotes on him:
Carlo Ancelotti: "Arrigo completely changed Italian football – the philosophy, training methods, intensity, tactics. Italian teams used to focus on defending but our team defended by attacking and pressing."
Roberto Donadoni: "Sacchi started a revolution in Italian football, both mentally and tactically. We developed our style of play and we tried to impose it on all opponents, from amateurs in a midweek training game to Real Madrid at the Bernabéu."
Xavi Hernández: "We are incredibly proud they compared us to Sacchi's Milan. That was a side that made football history."