Manchester United made a costly error in allowing Paul Pogba to leave for free in 2012. Buying him back for £89 million ($113m) was even worse, though.
However, it wasn't just a puzzling transfer from United's perspective. It never made much sense from Pogba's either.
The midfielder's agent, Mino Raiola, had always previously insisted that he would only leave Juventus for one of "the absolute top" clubs. Instead, he moved to Old Trafford, the aptly crumbling home of a once-great club that had fallen on hard times following the departure of legendary manager Sir Alex Ferguson.
At best, one could describe Pogba returning to Manchester as an emotional undertaking, an admirable attempt to settle some unfinished business at the club he had left in acrimonious circumstances. At worst, it was little more than a commercial venture, a lucrative money-making exercise for Pogba, Raiola and United.
Certainly, 'Pogback' felt more like an event than a football transfer, a glorified brand launch, with adidas celebrating the historic United deal with a social media music video featuring their client and rapper Stormzy.
Ultimately, though, it has proven a prolonged PR disaster for the player and it felt wholly in keeping with Pogba's time in Manchester that he announced his interest in seeking "a new challenge" elsewhere on a promotional tour in Japan.
Tellingly, many United fans will be relieved to see the back of him.
Pogba's perceived prima-donna behaviour has become so infuriating, so wearisome, that there is now even growing sympathy for maligned former Red Devils manager, Jose Mourinho, who repeatedly clashed with the Frenchman during their time working together.
Most memorably, there was a training-ground misunderstanding over an unfortunately timed social media post, as well as Pogba's infamous insistence on returning home from a game at Burnley in a chauffeur-driven Rolls-Royce rather than the United team coach – a remarkable episode that prompted Mourinho to amusingly refer to the 26-year-old as 'His Excellency'.
So, given everything that has happened in the last three years, why would Juventus consider taking him back?
Or, perhaps more accurately, why would the Old Lady consider paying a £150m transfer fee and a reported £15m a year in wages (£30m before tax) to beat Real Madrid to his signature?
First and foremost, if Juve were to sign Pogba, they believe it would make both financial and sporting sense.
They are, as a club, obsessed with winning the Champions League. It is why they signed Ronaldo last year, having decided that the acquisition of a 33-year-old forward could be justified on two grounds: firstly, that the Portuguese is a proven winner who remains in peak physical condition; secondly, the forward is a global phenomenon, meaning simply being associated with the 'CR7' brand would boost Juve's commercial pulling power.
In that regard, the acquisition of Pogba would only raise Juve's profile. He would also – along with free transfer Aaron Ramsey – add goals to a midfield that failed to pull its weight offensively last season.
Indeed, it is worth remembering that Ronaldo was the only Bianconero to score in the knockout stage of the Champions League in 2018-19. Pogba would undoubtedly help in that regard. He is, after all, coming off his most prolific campaign to date: 16 goals in all competitions.
However, what else would he offer Juve?
As Jorge Valdano pointed out while evaluating Madrid's interest in Pogba, "He is not a player who contributes much in the build-up." In that context, would he really be suited to Maurizio Sarri's intricate style of play?
Nobody is more familiar with Pogba's strengths and weaknesses than Juventus, though. They know from experience what he can and can't do.
It was they who realised that he is no No.10; that he is too ill-disciplined to play as a defensive midfielder or a regista; and that the only position in which he is truly effective is on the left-hand side of a three-man midfield.
And it is there that they would deploy him again, in Sarri's preferred 4-3-3 formation. On such a superficial level, it looks a perfect fit. But one wonders if Pogba would really flourish in a side playing one and two-touch football.
He likes to do as he pleases on the field and such characters don't often adapt well to ‘Sarri-ball’. As pundit Jamie Carragher pointed out last year, Pogba wouldn't have fit in at all at Barcelona, with their short, fast passing.
He could look just as out of place under Sarri in Turin, making him a colossal and unnecessary £150m gamble, when one considers Lazio powerhouse Sergej Milinkovic-Savic should be available for half that figure and Italy’s great new hope, Nicolo Zaniolo, would cost a quarter as much money.
What's more, Juventus are set to sign Paris Saint-Germain outcast Adrien Rabiot on a free transfer. In that context, he is a risk well worth taking – unlike Pogba.
Rabiot could solve Juve's desperate need for more quality in midfield, while at the same time freeing up funds to win the race to sign Ajax captain Matthijs de Ligt, which would address the Bianconeri's equally desperate need to rejuvenate their ageing defence.
Giorgio Chiellini is set to turn 35 this summer and Leonardo Bonucci, now 32, has struggled badly since returning to Turin from Milan a year ago. Behind them, there is only Daniele Rugani, who has not developed into the defender Juve hoped he would – even if a reunion with his former boss at Empoli, Sarri, could kickstart his career.
Cristian Romero of Genoa and Merih Demiral of Sassuolo both may be signed this summer, but Juve are crying out for a top-class centre-half like De Ligt to stabilise a back-line that was badly exposed in Europe last season.
The Dutchman would also come at half the cost of Pogba, with Juve closing in on a deal worth €70m (£63m/$80m) for the 19-year-old.
Moving beyond tactical and financial concerns, there is also the issue of Pogba's consistency and concentration.
When fully focused and motivated, he is almost unstoppable, as United fans discovered for approximately six weeks last season, following Mourinho's departure. However, he regularly went missing in some of the club's most important games.
Mourinho is, of course, biased when it comes to appraising Pogba but it was interesting to hear him argue that the reason why the France international looked such a different player at the 2018 World Cup was because he was shorn of the usual level of external distractions.
"I think the World Cup is the perfect habitat for a player like him to give the best," he explained on ESPN. "Why? Because it’s closed for a month, where he can only think about football."
It is a common criticism of Pogba's game, that he is as Carragher once argued, the kind of player who's "either 9/10 or 4/10. There is no in between with Pogba. I don’t think you can build a team around him because he’s so hit and miss."
The counter-argument, of course, is that Juve wouldn't be building a team around him.
Ronaldo is the undoubted star, while Miralem Pjanic will likely be tasked with pulling the strings in midfield; the 'Jorginho role', if you will.
Pogba, thus, would not be asked to run games – but merely influence them with his sudden, explosive bursts of creative quality.
It is a job he performed with aplomb during his first spell in Turin, when stationed alongside Andrea Pirlo, who provided the guile, and Arturo Vidal, the grit.
Certainly, 'Pogback: Part II' would most likely go a lot better in Turin than it did in Manchester. He would be joining a better team, be surrounded by better players and playing for a better coach.
The hard part, though, could again be convincing Juve's money-men that he is worth such a colossal investment.
Rabiot is poised to sign a deal worth €7m (£6m/$8m) a season, while De Ligt is set to earn around €15m (£13.4m/$17.1m) a year in wages.
Juve can, thus, ill-afford to take a £150m gamble on Pogba. Let Real Madrid have him. Don't make the same mistake as United.
Focus on De Ligt. He represents the future. Pogba belongs to the past.