Former Roma and Inter coach Luciano Spalletti realised Kalidou Koulibaly was something truly special less than two months after taking charge of Napoli.
"I have never worked with anyone so good," the Italian told reporters in July of last year, "not just as a player, but also as a man."
At the time, it seemed that club president Aurelio De Laurentiis was finally ready to cash in on his most prized asset.
The film producer claimed to have previously turned down an offer of €120m (£107m/$136m), such was his importance to the Partenopei.
However, the noises coming out of Naples last summer were that De Laurentiis was ready to do a deal while Koulibaly could still command a decent transfer fee.
After all, he had only just turned 30 and still had two years left on his contract.
However, no move materialised, much to Spalletti's relief.
Of course, another player may have sulked after failing to secure one last big move, but Koulibaly is not that kind of character.
Indeed, Spalletti quickly realised that the defender remained 100 per cent committed to the Napoli cause when Koulibaly went out of his way to return from international duty in time for a crunch Serie A clash with Juventus.
"Kalidou changed flights twice to speed things up," the Tuscan revealed in a press conference.
"Then got to the airport and went directly to the training ground without even stopping off home first.
"That's just remarkable!
"In terms of presenting practical examples that others can follow, he is excellent. If we all had a bit of Koulibaly, life would be easier."
Keeping clean sheets is certainly a lot easier for Napoli when Koulibaly is on the field.
Third-placed Napoli have lost just four times in Serie A this season – three of those defeats came while their best defender was sidelined by a thigh problem in December.
Spalletti's side fared well without Koulibaly while he was at the African Cup of Nations but even then he showed what they were missing.
Despite being laid low by Covid-19, which resulted in him missing Senegal's opening two matches in Cameroon, Koulibaly slotted seamlessly back into the starting line-up for their final group game and played every minute from then on as his nation lifted the trophy for the first time.
Koulibaly was immense in the tournament decider against Egypt, even netting Senegal's opening penalty in their shootout success.
As well as helping to keep Mohamed Salah quiet, he won possession more times (15) than any other player on the pitch, while also having the most touches (105), and making the most successful passes (81), perfectly illustrating why many consider him the most complete defender in the world alongside Liverpool's Virgil van Dijk.
There's been no Afcon hangover, either.
Koulibaly was at his brilliant best as Napoli held Barcelona to a 1-1 draw in the first leg of their Europa League knockout round play-off at Camp Nou last week.
In the run-up to the game, Diario Sport claimed that the Catalans were once again interested in signing Koulibaly.
The veracity of the report could be questioned but there's no doubt that Xavi's promising young side would benefit enormously from a leader of Koulibaly's quality.
Spalletti admitted after the game – which Barca only managed to level thanks to a dubious penalty awarded for handball – that he had run out of superlatives to describe the Senegal skipper, but gave it another go nonetheless.
"Scary," the coach said of Koulibaly. “I admire and hail Kalidou and the thing that amazes me now is his calmness and the level of authority he brings to the role.
"Koulibaly is always ready and he has this extraordinary ability to control games. So, that's why I would define him as scary."
Indeed, even Barcelona's fine forwards won't be looking forward to going up against Koulibaly again on Thursday night.
Of course, with another dominant display, the transfer talk would only intensify.
Koulibaly himself went some way towards alleviating the mounting tension at the Diego Armando Maradona Stadium by promising never to join Juventus.
"I could not betray the Napoli fans," he allegedly told journalist Valter De Maggio last September.
However, De Maggio claims that Koulibaly also admitted that he could be tempted into a transfer by three clubs: "Guardiola's Manchester City", Real Madrid and, most tellingly of all, Barcelona.
Napoli have not given up hope of persuading him to sign a lucrative renewal, with the latest reports also suggesting that he would also be given the captain's armband, with Lorenzo Insigne leaving this summer.
And if all else fails, don't be surprised if Spalletti again starts threatening to chain himself to Napoli's ‘scary’ superstar centre-back!