Sir Alex Ferguson has cited Ruud van Nistelrooy's reaction to being dropped for last season's Carling Cup final as the major reason behind his Manchester United exit.
Van Nistelrooy joined Real Madrid in a £10.3million deal last week claiming his relationship with Ferguson had completely broken down.
Despite scoring 150 goals in an amazing five-year spell at Old Trafford, Van Nistelrooy found himself overlooked for the latter stages of last term after losing out to Louis Saha in the battle to face Wigan in the showpiece final at the Millennium Stadium.
At the time, Ferguson claimed Saha deserved his place because he had played in most of the earlier rounds.
But it now transpires that not only was Van Nistelrooy upset by the move, the 30-year-old allowed his resentment to linger.
Ferguson said: 'The big difference with modern-day football is that now we have squads of players.
'It makes it difficult for a manager because every time you come to pick a team for a major game there are two or three players you are hesitant about telling they are out of the team either because they are great players, they have been great players in the past or you have a certain relationship with them.
'All you can do is hope they will agree with the reasoning behind your decision.
'Of course, sometimes a player doesn't agree. I am happy with that.
'But it what happens after that, how they adapt to it is different with every player. Ruud was different in that way. That is exactly what happened.'
Ferguson's comments, his first on Van Nistelrooy since the end of last season, emphasise why he made a veiled observation that the forward was becoming a disruptive influence in the dressing room.
Ironically, Ferguson delivered his verdict sat barely five yards from another Dutchman who left Old Trafford in acrimonious circumstances in Jaap Stam.
Now back in Holland with Ajax, whom United will face on Saturday in their second game of the prestigious four-team Amsterdam pre-season tournament, Stam was widely assumed to have been booted out by Ferguson because of controversial comments the defender made about some of his former team-mates in an autobiography.
Both parties were at pains to stress no hard feelings remain from the fall-out in 2001 which led to Stam joining Lazio.
'Jaap was a great player for me,' said Ferguson. 'He won the European Cup with me. But business is business. Sometimes, you get an offer you cannot refuse. That is the way it was.'
For his part, Stam insisted he bore no hard feelings towards his former manager and distanced himself from comments which suggested he retained a grievance about the way his departure was handled.
In fact, as he readily agreed, the deal probably worked out better for Stam given, unlike United, he has played in another Champions League Final since leaving England.
'The discussion about me leaving United has gone on for five years now,' he said.
'Sometimes, when a club gets an offer for a player, they accept it. That is the way it goes.
'Of course, maybe straight away you are not happy but you have to move on. I had three great years at Lazio and another two with AC Milan.
'I have no hard feelings. You could say it worked out well for me. I have had a good few years since leaving United.'
Stam's performances since quitting the Premiership have proved Ferguson was wrong to believe the defender's legs had gone and it has taken a long time for United to construct a defence which looks as formidable in his absence.
Ironically, Ferguson is currently facing the same problem attempting to cover Roy Keane's departure.
Michael Carrick, who is likely to make his debut against Porto tomorrow, has already arrived in a £16.8million move from Tottenham.
And, while he would not confirm a deal for Villarreal's Marcos Senna is near completion, the Scot did admit another new arrival is pencilled in for next week.
'We are looking at signing other players,' he said. 'Hopefully, something will happen next week.
'There is interest in Senna but there is interest in other players as well.'
Ferguson confirmed neither Cristiano Ronaldo, Mikael Silvestre nor Louis Saha had made the trip to Holland after only returning to training on Monday following their World Cup exertions.
In addition, Gary Neville is nursing a groin injury, while Gabriel Heinze and Nemanja Vidic are absent with knee problems.
'Gary and Gaby should be okay for the start of the season but I don't think Nemanja will,' said Ferguson.
'We will have to monitor the three lads who have just come back to see how they go.'