6 controversies Sir Alex Ferguson had as Manchester United manager

#2 Feud with Roy Keane

Keane (L) and Ferguson (R) did not part ways on the best of terms

A dominant box-to-box midfielder, Roy Keane was a warrior during his playing days, possessing aggression which saw him abhor losing and go all out in a bid to secure victory for his team.

For 12 years, Ferguson relished this side of Keane, as the Irishman proved to be an integral part of the United setup, even going on to become a fan favourite and captain of the team.

However, things began to go downhill between both men towards the middle of the last decade, as Keane continuously criticized the quality of the signings made by United.

Later through his biography, Ferguson revealed that it came as a relief to him when Keane departed for Celtic in 2005, as the then United captain was influential enough to have turned other players against Ferguson had he remained.

Their feud reportedly remains till this day, with Keane even going as far as to state that he regrets attempting to make peace with Sir Alex Ferguson.