Sir Alex Ferguson is recognised as one of the most combative and dominant managers of all time. A fiery presence on the sideline, he created some of the greatest - and most fierce - teams of the Premier League era - and according to former Manchester United goalkeeping coach Tony Coton, Sir Alex was just as dominant within the club.
Writing for the The Mail on Sunday, Coton recounted three times where the former United manager clashed with some of the club's biggest all-time stars - namely David Beckham, Roy Keane and Ruud van Nistelrooy.
According to Coton, it was not the infamous dressing room row between Sir Alex and Beckham which led to the latter's departure to Real Madrid; instead, it was the way the midfielder responded that saw the United manager decide to send him away.
By (likely) leaking the incident to the press, and then, according to Coton, playing up the cut he had received during the locker room argument, Beckham was making a power play against Ferguson:
"When [Coton] saw how staged the photographs were [he] realised Beckham's PR experts had gone for Sir Alex's throat. [Coton's] first reaction was: 'Close the door on your way out, David.'''
Yet Beckham was not the only high-profile player to attempt something of a power struggle with Ferguson.
Leading up to the 2005-2006 campaign, club captain Roy Keane was deeply unhappy with pre-season arrangements; Sir Alex invited family members to join the players as they trained, and Keane voiced his displeasure at the arrangement, even bringing it up during a team barbecue, much to the displeasure of Ferguson.
Things became so heated that Keane was not brought on the club's preseason tour of Hong Kong, China and Japan. Not long later, the Irishman left Old Trafford to join Celtic.
However, it was not always off-the-field issues that led to Ferguson having to assert his dominance - the decision to offload star striker Ruud van Nistelrooy came during the 2006 League Cup final.
The Dutchman was eager to come on, but as time passed, it soon became obvious he was not going to play. In response, the forward cursed out the manager, much to Ferguson's anguish.
According to Coton, Ferguson then told him:
"[Van Nistelrooy]'s finished here. No one speaks to me like that."
During the dressing room celebration after United's victory, Ferguson personally spoke to the Dutch striker. Soon after, he too was gone from the club.
Looking at these three cases, one things becomes clear; no matter how good a player you were, if you wanted to remain at Manchester United, you should never cross Sir Alex Ferguson.