David Beckham will not win any prizes for originality for pointing out that Sir Alex Ferguson is a great manager with a short temper.
Ferguson is feared and respected by United players in equal measure
But the England captain's autobiography underlines the extent to which Ferguson uses ruthlessness and his forceful personality to control his players, some would say obsessively.
As much as Beckham gave United over the years, Ferguson seems to have decided that the lifestyle of his most famous player brought his commitment to Manchester United into doubt.
It is too early to say whether Ferguson's decision to sell Beckham will come back to haunt him - and that judgement can certainly not be made on the back of one defeat for United and a goal for Beckham in his new role at Real Madrid.
Ferguson, though, has a track record of making decisions about players based on his personal relationship with them as well as their ability.
Several times, Ferguson has exercised his authority by selling a valuable player who the Scot believed had undermined him.
But several times he has also stuck by men who many outsiders believed had gone beyond the pale.
Here we examine the complex decision-making of the most successful manager in British football.
After two unsuccessful seasons in charge at Old Trafford, Ferguson made what were arguably his first big decisions as Manchester United boss.
He had pinpointed the team's drinking culture as the crucial thing holding the club back, and he sold two of the men at the heart of it and the team - defender Paul McGrath and striker Norman Whiteside.
It was not a popular decision, and United's mixed performances in the old First Division for much of 1989-90 did not help his case - but Ferguson ended the season with his first trophy at United, the FA Cup.
The team's flawed heart
Ferguson's talismanic captain Roy Keane has his fair share of personal demons - the Irishman reveals his drinking binges and struggles with alcohol in his autobiography, admitting how they exacerbated his injuries.
And Keane's disciplinary problems, which the player admits often came about through a disinclination to control himself when he should have known better, would have been too much for many managers.
Ferguson has been prepared to overlook Keane's disciplinary problems
Yet Ferguson has never stinted in his support of Keane, whose total commitment to winning matches that of the manager.
For that - combined with his ability as one of the greatest midfielders in the world - Ferguson was prepared to forgive him his failings.
Keane's performances down the years make it difficult to question that decision.
After winning the Premiership two years in a row, United were pipped to the title in 1995 by Blackburn Rovers.
Most blamed the loss on the absence of Eric Cantona, but Ferguson decided to sell three of his key players - midfield dynamo Paul Ince, winger Andrei Kanchelskis and striker Mark Hughes.
Ince's ego was his downfall in Ferguson's eyes
The Ince decision caused consternation among fans, but it was typical Ferguson.
The manager accused him of letting the team down in big games, but just as important was that the England star was getting too big for his boots in Ferguson's eyes.
Among other things, Ince had insisted on being called by his nickname "The Guv'nor" by everyone - including Ferguson, whose thinking was illustrated in a TV documentary in which he called Ince a "big-time Charlie".
The decision to replace these stars with a number of then-largely-unknown young players - Beckham, Paul Scholes, Nicky Butt and Gary and Phil Neville - led BBC pundit Alan Hansen to say: "You don't win anything with kids."
Another Premiership title forced Hansen to eat his words.
Giant Dutchman Jaap Stam was the key figure at the heart of United's defence when he published his autobiography at the start of the 2001-02 season.
The book contained a number of critical observations about Ferguson in particular and United in general, and a few weeks later Stam found himself sold to Lazio.
The decision came after he had made a poor start to the season, and Ferguson said it was made for footballing reasons and had nothing to do with the book.
Stam was not happy about being transferred to Lazio
But few believed him.
Stam was replaced by veteran Frenchman Laurent Blanc, who appeared past his best and shouldered much of the blame for United ending the season without a trophy with their poorest defensive record for years.
The more committed United fans might argue that was unfair, for the team still reached the semi-finals of the Champions League.
But it was not until Blanc became a peripheral figure last season after the signing of Rio Ferdinand and the emergence of John O'Shea that United's defence reclaimed its former solidity - and the team grabbed back the Premiership.
The tortured genius
Enigmatic, hot-tempered Eric Cantona had proved too much for a succession of managers at club and international level, but Ferguson was prepared to take a risk when he poached him from Leeds in 1992.
The Frenchman was indulged at Old Trafford in a way that surprised many, but which seemed to be rooted in Ferguson's knowledge that his complexities and problems came hand-in-hand with an improvisational brilliance matched by his will to win.
The crunch moment came when Cantona was banned for kung-fu kicking a spectator who was abusing him when he was sent off in a match against Crystal Palace in early 1995.
Cantona was indulged and cultivated despite his dark side
There were calls for him to be banned from football forever, but Ferguson stuck by him and believed him when he said he would change.
Cantona returned from his ban to lead United to two more Premiership titles and the FA Cup before announcing his retirement while still at the height of his inspirational powers.