It was a cold, rainy afternoon in Montpellier when Arsenal first became serious about William Saliba. This was 2019, before the scouts, agents and rival clubs would descend en masse. He was playing for Saint-Étienne’s under-19s and Ty Gooden, then Arsenal’s France scout, had alerted them to the raw yet impressive 6ft 4in 18-year-old working his way through the ranks. His insistence had brought Francis Cagigao, then the club’s head of scouting, to the south of France.

Cagigao and Gooden initially had their eye on another centre-half at Saint-Étienne, a year older and already in the first team. He will also be playing on Sunday at Stamford Bridge, against Saliba. Indeed, the older centre-half would eventually command a £70m transfer fee. However, it was Saliba’s extraordinary speed and presence that attracted the Arsenal duo over Wesley Fofana.

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Saliba impressed in that game but also picked up an injury, meaning it was six weeks before Arsenal could return to watch him again. After the second sighting, Cagigao called Raul Sanllehi, then Arsenal’s head of football. “We have to sign this boy,” he said.

That moment is football’s equivalent of discovering the holy grail. A scout’s lot is to hope perpetually amid endless disappointing midwinter trips watching young teenagers at nondescript training grounds. But the ones that stand out make the job worthwhile. Cagigao was also the first Arsenal representative to lay eyes on Cesc Fàbregas, a moment a scout lives for.

In essence, it is what Todd Boehly and Behdad Eghbali have attempted to implement at Chelsea, with mixed results: a recruitment system so smart it takes the most talented teenagers off the market before they are well known.

Arsenal seem to have managed it better. Saliba, along with his centre-half partner Gabriel Magalhães, also scouted by the Gooden-Cagigao combination, and Gabriel Martinelli, discovered by Arsenal’s former Brazilian scout Everton Gushiken and driven through by Cagigao, are three jewels unearthed for relatively low fees and now worth significantly more.

“You can be the best centre-half in Europe,” Cagigao was telling a bemused Saliba at Arsenal’s London Colney training ground a few months after that initial sighting. Saliba, still only 19, had only just made his Saint-Étienne first-team debut but was now at one of the biggest clubs in the world, with Cagigao going through his strengths and weaknesses, showing him data on his matches and where he might improve, how Arsenal could help him. Given he had played most of his games for Saint-Étienne II and the under-19s, it was impressive Arsenal could demonstrate they knew him so well.

Herein lies the weakness of a youth recruitment model largely reliant on data: for the youngest players, there often isn’t anything meaningful to analyse. “With young players you have to wait a certain amount of games before you can say something reliable with the data,” says Ian Graham, who was Liverpool’s head of research, helped to build their 2020 title-winning team and runs the consultancy Ludonautics. However, the trick is to sign a player before the mainstream and meaningful data shows he is good, because at that point every club in Europe is tracking him. It’s high risk yet, if you get a player of Saliba’s calibre, high reward.

Even then, making a player and agent feel loved and appreciated is the key to recruitment. Amid the cold analytics, hearts need to be won as well as minds. After the presentation to Saliba, Huss Fahmy, at that time Arsenal’s head of football operations, and Cagigao took the player and his agent Djibril Niang to Sushisamba, the fusion restaurant located on the 38th and 39th floors of the Heron Tower in the City of London, with spectacular views of the capital. Far from the suburban sleepiness of London Colney, the bustle and energy at the heart of the capital was designed to impress a teenager and did the trick.

At that point, Tottenham became interested but were wasting their time because Saliba and Niang were sold on Arsenal. The presentation had been key. One person who was close to the deal said: “That absolutely made the difference, one million per cent. A player and agent these days need to know you’re more than just financially invested in them but know their game and can help them progress.”

Spurs’ interest was still an unwelcome complication for Arsenal and a gift for Saint-Étienne, pushing the price from £12m to £18m with add-ons of up to £7m. Understandably the Arsenal scouting team came under intense pressure with the increased price. Were they really still sure about this unheralded teenager? At that price? “Sign him!” they insisted.

With the departure of Edu from his role as sporting director being announced this past week, Arsenal fans can perhaps take some solace from the Saliba signing. It is not that Edu will not be missed, but the common perception that he masterminded the Saliba deal is some way from the full story. Saliba signed two weeks after Edu arrived in 2019 yet the deal had been in the making months before he had agreed to take the job, as had that for Martinelli, who also joined that month.

In fact, the scouting team that helped set up those deals would be swept away in a fresh approach to recruitment at Arsenal a year later. Yet their legacy was to gift the club one of the world’s finest centre-halves. Doubtless Boehly and Eghbali will watch and learn on Sunday afternoon as they attempt to repeat the trick rather than pay £70m for their next promising young centre-half.