What if the hottest property in modern football wasn't Kylian Mbappe or Matthijs de Ligt, but a balding, bespectacled 54-year-old who hasn't laced up his boots in over 30 years?

As the man who helped to launch the careers of players such as Fabinho, Bernardo Silva, Thomas Lemar, Anthony Martial and Nicolas Pepe, Luis Campos has established a reputation as one of the game's leading talent-spotters.

The list of clubs rumoured to have shown an interest in the Lille sporting director's services reads like a Who's Who of the European elite, with Manchester United, Arsenal, Chelsea, Barcelona, Real Madrid, AC Milan, Roma, Paris Saint-Germain and Marseille all reported to have sounded him out about the possibility of becoming their sporting director in recent years.

"It's not a coincidence that his name has been linked with Chelsea or Milan or the other top clubs in the world," says Aitor Karanka, who became friends with Campos while working alongside him at Real Madrid.

"When you look at the players who he signed at Monaco and Lille, the difference between the price they had and the price they have now is amazing. He's one of the best."

Even before he had laid the foundations for Monaco's sensational Ligue 1 title win in 2017, Campos was a source of fascination in France, with headlines variously describing him as "the invisible man" or "the mysterious Mister Campos."

Having followed up his successes at Monaco by helping to propel Lille into the Champions League, Campos now enjoys a much bigger profile, but despite the occasional television appearance, an air of mystery remains. So who is the man with the Midas touch in the transfer market? And what are the secrets of his phenomenal hit rate?

Before he became one of football's leading transfer masterminds, Luis Campos was a manager. And not a very successful one.

Born in Fao, a small coastal town of 3,000 people in northern Portugal, Campos played football throughout his youth before going on to study physical education at the University of Porto—a course that took him down the same path as his compatriots Jose Mourinho and Carlos Queiroz, who attended the University of Lisbon.

While pursuing his studies, he turned out for local club AS Esposende and tried his hand at youth coaching. After graduating, he hung up his boots and joined SC Espinho—then playing in Portugal's top tier—as a fitness coach. From Espinho, he went to Uniao de Leiria, initially working as an assistant coach and then, at the age of just 27, becoming manager.

Over the 13 years that followed, he would take charge of a succession of modest Portuguese clubs. His teams were renowned for the good quality of their football, and he occasionally made the headlines, such as when his Gil Vicente side ended Mourinho's unbeaten 27-game start to the season with Porto in April 2004.

But the thing Campos was most famous for was getting teams relegated. In the 2002-03 campaign, he contributed to the demotions of two clubs—Vitoria de Setubal and Varzim—and in 2004-05 he repeated the trick with Beira-Mar. It earned him the nickname "Luis Campas"—campa being a Portuguese word for "grave."

Nevertheless, the players who played for him recall a manager who fizzed with energy and ideas and who always went out of his way to make them feel supported.

"He was very straightforward, he was hard-working, he was passionate about football and he had that human side that helps to get the best out of players," says Ali El Omari, who played under Campos at Gil Vicente and Beira-Mar. "He's left a good impression with most of the players he's worked with."

After leaving Beira-Mar in 2005, Campos turned his back on the dugout. He started teaching and invested in a beachside restaurant in Esposende, but thoughts of football were never far away.

Along with another former coach, Americo Magalhaes, he set up Training to Play (T2P), a company that provided equipment, training DVDs and tactical software for football clubs. One of their innovations, an application called the Mourinho Tactical Board, was custom-made for the man it was named after. United by mutual admiration, Campos and Mourinho had become close allies.

Campos also earned the trust of super-agent Jorge Mendes, and the scouting work he undertook for Porto further enhanced his reputation as one of the sharpest minds in the Portuguese game.

After seven years without an official position in football, Campos made a triumphant return in July 2012 when Mourinho invited him to join his backroom staff at Real Madrid. It was the ultimate riposte to his detractors.

"It was not by chance, because I have blue eyes or because I'm beautiful," Campos told Portuguese newspaper O Jogo in 2016. "I was invited because Jose Mourinho understood that I had the competence to work with him."

Anyone walking past Campos' office on the ground floor of Madrid's Valdebebas training centre could have been forgiven for thinking it looked more like it belonged to a Silicon Valley tech guru than one of the world's leading football scouts.

There were no piles of notepads, no bulging files, no overflowing drawers. Instead, all of Campos' data was meticulously collated on his laptop and iPad. He kept his office clean and tidy. There were photos of his wife and two daughters, as well as a picture of Campos astride a mountain bike in a nod to one of his hobbies.

One of Campos' recommendations arrived at Madrid shortly after he did. Brazilian right-back Fabinho, a loanee from Portuguese side Rio Ave, would make only one first-team appearance at the club, but after being reunited with Campos at Monaco a year later, he developed into a €50 million central midfielder.

"He's the kind of player now, when you see him playing at that level [with Liverpool], you realise how good Luis is," Karanka told Bleacher Report.

Campos' colleagues at Madrid were disarmed by his enthusiasm, his diligence and his energy. He used his time at the club to develop a new piece of scouting software, Scouting System Pro, and was never afraid to offer an opinion.

"Luis works in a lot of detail. He's very persistent and always looks for as much information as he can find," recalls Jose Morais, who was one of Mourinho's assistants at Madrid. "He's a guy with ideas who's dynamic enough to make things happen. He's a kind of entrepreneur."

Campos, who speaks several languages, was employed to help Madrid identify promising players, and he doubled up as an opposition scout. A central tenet of his approach is his belief that there is no substitute for watching players in the flesh, which means he spends much of his life in taxis, airports and hotels.

"For me, live observation is fundamental," he explained in a 2017 interview with Duncan Castles for Yahoo. "For example, a small detail such as observing how a player warms up before a game or coming on as a substitute reveals much of his character. And character is an essential marker in detecting a top talent."

Armed with his ever-expanding library of player data and invigorated by the experience of working alongside Mourinho, Campos left Madrid for Monaco in 2013, initially acting as an advisor to club president Vadim Vasilyev and then, in August 2014, becoming technical director. (He also—briefly—tried his hand at international football in 2014, working as an opposition scout for the Argentinian national team at the World Cup in Brazil.)

Campos' change of job title coincided with a sharp shift in Monaco's recruitment strategy. The club spent lavishly in the 2013 summer transfer window—shelling out around €150 million on proven stars including Radamel Falcao, James Rodriguez and Joao Moutinho—but the following year, owner Dmitry Rybolovlev decided such huge expenditure was unsustainable. It was then that Campos came into his own.

Using his extensive networks, he set about assembling a squad of up-and-coming young players, all of whom had significant resale value. Bernardo Silva came in from Benfica for €15.75 million, Tiemoue Bakayoko from Rennes for €8 million, Fabinho from Rio Ave for €6 million, Lemar from Caen for €4 million and Benjamin Mendy from Marseille for €13 million. All would later be sold for vastly higher fees.

Campos had left for Lille by the time Leonardo Jardim's Monaco team romped to the title and reached the Champions League semi-finals in 2017, fired by the goals of Falcao and youth-team graduate Mbappe, but his fingerprints were all over their success. The players he brought to Stade Louis II would help the club to generate close to €1 billion from incoming transfer fees.

Campos vowed, as Monaco closed in on the title, that he would create "other masterpieces" in his career, and last summer's transfer window at Lille stood in comparison with any of the dazzling brushwork he produced in the principality.

Having clashed with Marcelo Bielsa over the club's recruitment policy during the Argentinian's blink-and-miss-it tenure as head coach, Campos has played a central role in Lille's renaissance. The cash-strapped club spent a measly €8.9 million on transfers last summer—their shrewd acquisitions including Jose Fonte (free), Zeki Celik (€2.5 million), Jonathan Ikone (€5 million), Jonathan Bamba (free) and Rafael Leao (free)—but the team Campos helped to assemble spectacularly outperformed expectations under Christophe Galtier, going from relegation peril to Champions League qualification in just 12 months.

For El Omari, his former protege, Campos simply possesses an innate ability to spot good players. "Luis doesn't need to see 50 matches [to assess a player's worth]," says the former Morocco international. "He has a gift."

Karanka believes it boils down to a combination of knowledge, experience and motivation.

"He's been in football for a while in different areas: scout, coach, sporting director," says the former Real Madrid centre-back. "And he's very enthusiastic about his job. His passion is the key. If you spend one hour with him, you can be sure that for one hour he'll be speaking about football."

Lille have already sold Thiago Mendes and Youssouf Kone to Lyon for a combined fee of €35.5 million this summer, and Pepe is also expected to leave for as much as €80 million. But the one that everyone really wants, of course, is Campos.