Sir Alex Ferguson's decision to let Paul Pogba go in 2012 has proved very costly - both figuratively and literally - for Manchester United.
Having struggled for game time under the Scotsman, Pogba opted for pastures new and joined Juventus on a free transfer, with United receiving £800,000 in compensation.
At that moment, no one could have predicted what would happen four years later, with Pogba rejoining Jose Mourinho's United for a world-record £89 million.
A very expensive mistake indeed.
United have the money to do it, of course. Any player can be sold at Old Trafford in the knowledge that they can comfortably be re-signed in the future.
Just look at Memphis Depay. The Frenchman joined Lyon in January for £16 million, but United included a buy-back clause in his contract in case he realises his vast potential.
Any future move could cost the Red Devils in excess of £50 million should Depay live up to expectations and become world class.
Re-signing former players clearly isn't below United and with that in mind, Rio Ferdinand has named the former Red Devil he would like to see return in the near future.
In a recent interview with BBC 5 Live, Ferdinand explained how one former United player has the potential to be a "huge star" like Pogba.
That player is Burnley centre-back Michael Keane.
"[Keane] likes to ask questions, he likes constructive criticism and that's a great attribute to have," Ferdinand said. "To be there, to look at your game in detail and try and improve.
"He's always wanting to improve, whether it's nutrition, whether it's physical, whether it's actual working on your game after training. He was always wanting to learn and understand more.
"I think the moment he found out he was going to leave Manchester United - every kid's dream in that area is to play for Manchester United - so to leave the club was a huge wrench for him.
"But it allowed him to go and spread his wings and bloom really and become the player he is now. At Manchester United he wasn't afforded that opportunity, for whatever reason.
"You look at the likes of Pogba; he's gone away and come back now and become a huge star. Michael Keane, he could do that himself."
A somewhat bold statement from Ferdinand, but Keane, 24, has shown huge promise since joining Burnley in 2015 and guiding them into the Premier League.
The only issue is where the Englishman would fit in at United, who already have plenty of options at centre-back.News Now - Sport News