9. Roy Keane & Patrick Vieira
Source: Telegraph
Keane has made several enemies during his successful career, but the most well-known are the long-standing rival with Vieira. The two played for the top two teams in England, Manchester United and Arsenal, so there is expected competition. Their feud started in 2005 in the tunnel before a match, where Keane believed Vieira was bullying Gary Neville, and he came to his defense.