Arrigo Sacchi still regrets returning to AC Milan in December 1996.
During his first stint at San Siro, between 1987 and 1991, he won a Scudetto and two European Cups with one of the finest sides the club game has ever seen.
His second spell would not be so successful, with Sacchi parting company with Milan after just over six months in charge, in the wake of a dismal 11th-placed finish in Serie A.
Sacchi had known that Milan were in a bad way when he took over, but he grossly underestimated the enormity of the rebuilding job, particularly in terms of the quality and mentality of the players.
Just two weeks into his return, he told the club's directors: "You want to cure a tumour with an aspirin. It won't work."
And it didn't. It rarely does, in truth.
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Massimiliano Allegri, though, clearly believes that he can make a success of his return to Juventus, which was confirmed by Goal on Thursday.
And there are grounds for optimism. After all, Allegri arguably knew before anyone else that Juve needed an overhaul.
In 2019, after his fifth successive Scudetto, and the club's eighth in a row, the Tuscan urged Bianconeri president Andrea Agnelli to revamp the squad.
According to the Gazzetta dello Sport, he had even told his boss to "get rid of (Cristiano) Ronaldo", who had only joined from Real Madrid the season before.
There was never any chance of that happening, of course. As Agnelli himself had admitted, the Portuguese superstar hadn't merely been signed for sporting reasons; there were also economic factors involved.
In the end, it was Allegri who was forced out, with Fabio Paratici the key protagonist in his departure.
Indeed, as soon as it was confirmed on Wednesday that Paratici's contract as sporting director would not be renewed this summer, it was clear that the path was being paved for Allegri's return.
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The fans are understandably enthused.
Firstly, there's the fact that bitter rivals Inter wanted to hire Allegri after having their world turned upside down by Antonio Conte's resignation.
Secondly, and far more importantly, Allegri already knows Juve inside out. It was he who took them closer than anyone over the past 25 years to winning a third European Cup.
As well as recording four domestic doubles, Allegri's team also reached two Champions League finals, in 2015 and 2017.
This is where it gets interesting, though, because Juve no longer have anything like the same quality, particularly in midfield.
There has been a general regression since Allegri's departure in 2019. An inability to reach the semi-finals of the Champions League even with Ronaldo leading the attack represents irrefutable evidence of the Old Lady's decline.
Allegri's successor, Maurizio Sarri, managed to retain the Serie A title in his one and only tumultuous season at the helm but Juve didn't play with anything like the style the former Napoli boss had been hired to provide.
Less than 24 hours after dismissing one of the most renowned tacticians in Italy, the Old Lady turned to a complete novice in Andrea Pirlo and that decision proved predictably calamitous.
The former midfielder may have lifted the Coppa Italia but if Napoli had beaten Verona on the final day of the Serie A season, Juve wouldn't have even qualified for next season's Champions League.
For many, though, Pirlo wasn't the problem, or at least not the primary problem.
There has been a distinct lack of coherent thinking at Juve over the past two years, resulting in an imbalanced squad which some experts feel no longer has the same level of determination that drove the Bianconeri through an unprecedented era of success.
"Motivation is like petrol for a car," Sacchi wrote in the Gazzetta dello Sport. "If you don't have it, you can't start the car. You can be sitting in a Ferrari, but without the fuel, you can't go anywhere."
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Allegri's return could obviously reignite the club. There's no doubt that the likes of Paulo Dybala and Giorgio Chiellini will be delighted to see him back. Indeed, Goal has learned that Allegri has already instructed Juve to tie Dybala down to a new contract.
The 53-year-old's appointment could also aid Juve's pursuit of former Milan players Manuel Locatelli, now at Sassuolo, and Gigi Donnarumma, who has just quit San Siro and is available on a free transfer.
There's certainly no way Allegri would have agreed to return to Turin without assurances that the squad would be strengthened over the summer.
Like many other elite clubs, Juve have financial problems, which is why Agnelli is refusing to give up on his beloved European Super League, but the removal of Ronaldo from the wage bill could ease some of their economic concerns.
The forward posted what many fans feared was a coded farewell last weekend and a parting of the ways a year before the expiration of his contract is probably the best option for both Ronaldo and Juve right now, even if finding a buyer would be far from straightforward.
His goals would be sorely missed but, no matter what happens, it's clear that the new Juve needs to be built around the likes of Dybala, Matthijs de Ligt, Federico Chiesa and Dejan Kulusevski.
Allegri has never publicly criticised Ronaldo, even after leaving Juve, preferring instead to speak very diplomatically about coaching the five-time Ballon d'Or winner.
However, Ronaldo was very open about the fact that he preferred Sarri's more attacking brand of football to Allegri's very pragmatic approach. It is also worth nothing that he only scored 21 times in Serie A during his one season under the former AC Milan coach. That total reached 31 under Sarri and 29 with Pirlo.
Ronaldo, then, may not be as enthused as the supporters by the change of coach.
It's undeniably a bold move. Juve have gone full circle by rehiring Allegri. It is essentially an acknowledgement that they have erred badly with their past two appointments, so it is hard to have too much faith in a board that has made so many wrong moves in the past couple of years.
Allegri, though, was undoubtedly the best possible option for a club in dire need of stability – and a top-class coach. After all, it wasn't just Inter who sought his services; Real Madrid wanted him too.
On the face of it, Allegri's return is a step backwards but it could actually get Juve moving in the right direction again.
Unlike Sacchi's return to San Siro, Allegri's second stint in Turin might just work. With or without Ronaldo.