Sir Alex Ferguson has labelled the decision to announce his retirement in 2001 as the biggest mistake of his managerial career.
The Manchester United manager had been in charge for 15 glorious years at the time and announced in the summer that the 2001/02 season would be his last in charge.
He had been in talks with chief executive Peter Kenyon but when they collapsed, he went public with his intentions to leave his Old Trafford post.
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It wasn't until January that Ferguson rescinded the decision but by that time he had already caused massive disruption within the squad.
He would, of course, go on to spend another 11 years at Manchester United, sealing his place as one of the game's greatest ever managers.
Although everything turned out fine in the end, Ferguson, now three years into his actual retirement, believes his decision in 2001 remains his biggest regret.
“The biggest mistake I made was announcing it at the start of the season," Ferguson admitted to The Mirror.
"I think a lot of them had put their tools away. They thought, ‘Oh, the manager’s leaving’, but when I changed my mind in January, I started thinking about United again and how we could get back on top.”
Because Ferguson was set to leave, Manchester United had problems recruiting players in the transfer window while their star players were distracted by the uncertainty.
The Red Devils finished third in that campaign with Arsenal trumping them by a significant 10 points. Having crashed out of both the FA Cup and the Champions League, Ferguson realised he could not leave without first ringing in a new era of success.
He added: “In 2005, that period we didn’t win anything, just before that I had an attempted retirement and that affected everyone. It was a mistake and my wife and my three sons changed my attitude towards it and I started to think again.
“After that is when Wayne Rooney and Cristiano Ronaldo came to the club and we had to regenerate everyone. The youth side of it, the scouts, we’d gone to sleep.
“Strangely enough, the period from there on has been glorious – it’s been fantastic with the numbers of league titles we won. The moments you don’t win anything register very strongly.”