When Liverpool agreed a headline-grabbing €33 million (£28.3m; $38.3m) deadline-day deal for 18-year-old Lucca Brughmans, the transfer made him the most expensive teenage goalkeeper in football history. Just a year earlier, Chelsea spent €20 million to recruit 19-year-old Mike Penders. Both follow a well-trodden pathway from the eastern Belgian town of Genk straight to the pinnacle of world football.

Genk has quietly cemented itself as Europe’s most prolific goalkeeping assembly line. Over the past two decades, the club has produced Real Madrid and Belgium star Thibaut Courtois, RB Leipzig first-choice Maarten Vandevoordt, and Saudi Pro League goalkeeper Koen Casteels. Linking every single breakthrough is one man: veteran goalkeeping coach Guy Martens, whose association with the club stretches back nearly 35 years.

The Evolution of the ‘3D Goalkeeper’

Martens, a former schoolteacher who took over first-team goalkeeping duties at Genk in 1990 without formal specialist training, developed his philosophy through continuous innovation inspired by Dutch methods, notably Frans Hoek’s work at Ajax.

At the core of Martens’ framework is the concept of producing ‘3D goalkeepers’ rather than traditional ‘2D’ shot-stoppers.

“Before Hoek, goalkeeper training was always three goalkeepers in a row, popping up shots in the corner of the pitch,” Martens explained. “In 2D, a goalkeeper simply performs the action, like a save or a punch. To be proactive, you must have the ability to play football. To be 3D, you have to dominate, to always be the boss of every ball coming into the space. Always have good game reading, always have good decision-making. For me, a goalkeeper plays a fantastic game when he doesn’t make any save. It means his positioning must be fantastic.”

No Full-Time Keepers Before Age 12

This distinct ideology has shaped unconventional training methods. In Genk’s junior academy ranks, no player is recruited exclusively as a goalkeeper before the age of 12. Instead, all academy players rotate through the position while developing outfield skills, game vision, and technical agility.

“Before Courtois was 12, he played outfield,” Martens revealed. “I’ve never had a good goalkeeper who played in goal since they were six years old. In 3D, they need to know what it’s like to play high, to play up front, to be in midfield. In my view, the goalkeeper is the first attacker and the last defender. That technique is easy to learn. But the vision? You have it or you don’t.”

Genk youth goalkeepers also wear mandatory protective scrumcaps to emphasise cognitive development. Specialised training is heavily integrated with outfield players in simulated real-game scenarios, strengthening neural decision-making pathways.

“The development of your brain is about making connections through tiny electrical threads,” Martens said. “If you repeat something a lot, the connection gets thicker. If I’m just kicking the ball at them, because it’s only me shooting, they know what’s going to happen. They don’t have to make decisions.”

Patience and a No-Blame Culture

Martens avoids premature physiological testing, noting that young prospects develop at wildly different rates. When Courtois was 13, some academy coaches pushed to release him due to coordination struggles before a growth spurt and mental resilience helped propel him to a senior debut at 16.

Similarly, Martens has instilled a strict no-blame culture to remove the fear of errors. When Vandevoordt was dispossessed attempting a Cruyff turn on his Champions League debut at Napoli in 2019—becoming the competition’s youngest-ever goalkeeper—the club stood firmly behind him.

“We never blame them if they make mistakes,” Martens said. “If they made a mistake when they were being proactive, fantastic. It is my fault, not theirs.”

Genk structure their first-team squad with four goalkeepers, guaranteeing at least two under the age of 18 train alongside established professionals. The club accepts that young stoppers will make high-profile errors on the pitch, safe in the knowledge that elite clubs will routinely arrive with lucrative offers.

“Everybody in Genk knows that they’ll make mistakes,” Martens added. “And then, always, before they turn 21, they’ll go away for €10million, €20m, more. So then they say, ‘OK, Guy, who’s next?’”