#1 Pep Guardiola
Arguably the most successful coach in Barcelona's history and the greatest manager in Messi's entire career. Pep Guardiola had the most influence on Lionel Messi's footballing career. The tactical genius was the coach at FC Barcelona between 2008 and 2012.
It is true that Messi's most successful years came under Pep Guardiola. With the manager's possession-based system, the Argentine superstar flourished. He was deployed as a playmaker occupying the famous false 9 position for most of their time together.
They won many trophies including 2 UEFA Champions League and 3 La Liga trophies. Messi also won 4 consecutive Ballon d'Or awards under the manager.
Pep Guardiola's ambitious nature drove him out of Spain to join Bayern Munich but he will always be remembered by his little genius, Lionel Messi.
Please note that this list is Opinion-Based.