Manchester derbies have always been a fierce encounters, and nothing was fiercer than watching Roy Keane fly into the knee of Alf Inge Haaland back in 2001. The tackle is one of the most disturbing ones in the history of the Premier League, in which Keanes deliberate actions ended the career of Haaland. The backstory to this tackle makes the events even more horrific. In a match several seasons before the 2001 incident, Keane had injured his own knee when viciously tackling the defender. With Keane out of action, Haaland told the aggressive Irishman to get up and stop pretending. Keane's response came years later by ending Haalands career.