No one at Manchester United needs to be told that letting Paul Pogba leave for next to nothing in 2012 was a huge, huge mistake. But that is exactly what former defender Rio Ferdinand has done.
The 23-year-old midfielder left for Juventus under the freedom of contract rule four summers ago and has since become one of the best players in the entire world. In fact, he is so good that United are ready to pay £100m to bring him back to Old Trafford.
Having lost him for just £800,000, it is certainly what one could call a costly mistake. For Sir Alex Ferguson, it is a major tarnish on his otherwise incredible legacy as Manchester United manager.
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But Ferdinand has claimed that Ferguson could have avoided the error had he paid attention to his dressing room. According to the BBC pundit, every single person in the Old Trafford dressing room knew they would eventually regret letting him leave.
Speaking to the BBC, he said: "His star quality was undoubted. There was not one person in that changing room who wasn't sure. Everyone in that changing room knew that him leaving was a huge, huge error."
So for those Manchester United fans saying "Ah well, Fergie didn't know he would go onto to become a ridiculous player at Juventus", please stop now. It is clear the Scots ego got the best of him on this occasion.
But what stood out?
Ferdinand delved deeper into his box of Pogba-related anecdotes and explained exactly why he believed the Frenchman, then just 19, was destined for greatness.
He said: "This is potentially the £100m kid at 23 years old, he's got huge potential. The thing that stood out for me when I first met him other than he ability was his personality."
What appears to have impressed Ferdinand the most is the way Pogba has dealt with the levels of expectation at this summer's European Championships. Pogba was the poster boy for the tournament, hosted in his native France, and much was expected of him.
After a tricky start, Pogba has grown in stature throughout the tournament and played a key role leading them to the final.
He continued: "This kid wants to be the best, he started this tournament very anxious, like a kid who had something to prove after he'd been hyped up and was worthy of that hype but he's grown into this tournament.
"He's really grown in stature in the tournament and they rely on him in many areas. He's the poster boy of this tournament, there's a lot of pressure on his shoulders and he's got a fantastic future."