During his time at Manchester United, the recently retired Keane established himself as Alex Ferguson's greatest ever signing; and also by far his most unstable. As if it wasn't enough admitting in his autobiography to exacting revenge on an opponent, Roy also publicly stuck the boot into his own fans, team-mates and most famously, the Republic of Ireland manager.

He might say: "Vieira? I'll have him!"

He won't say: "I really didn't mean what I said earlier…"

Anger factor: 10/10