Samuel Eto'o's illustrious playing career has seen him cross paths with the coaching duo at three separate clubs - more than anyone else on this list. The Cameroon striker was already an established name when Pep Guardiola was handed the Camp Nou job in 2008. Although he contributed 36 goals to a treble-winning campaign, he was constantly at odds with the Spaniard. Earlier this year, Eto'o branded him a coward, claiming: "Pep told me how to move like a striker. I told him: 'You're not normal!' The true story is that Pep didn't respect the things in football."