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Attempting to understand genius, and all its forms, is one of football's great debate starters.

There are those who will argue that the truly inspired are the beneficiaries of what is called 'God-given talent' suggesting that some kind of alchemy has been passed on to sacred individuals as they await their entrance to the mortal realm. To the more secular mind, attempting to reduce a deliciously curled free-kick or a mathematics-defying reverse pass to something conjured up in a heavenly domain seems preposterous.

A new book The Number Ten: More Than a Number, More Than a Shirt attempts to answer some of the questions about what makes the best No.10. The book's author Andy Bollen (A History of Scottish Football in 100 Objects, Fierce Genius: Cruyff's Year at Feyenoord and A History of European Football in 100 Objects)says it requires “many special qualities” to be a No.10, a shirt that has assumed mythical proportions in the game.

Bollen points out that there is not just one secret ingredient found in the petri dish that has produced some of the best footballers of all time but there are many similarities with work ethic, adversity, determination and mental strength chief among them. In the book, Bollen documents the lives and playing careers of all the men (and one woman) you would expect to read about: Pele, Diego Maradona, Lionel Messi, Zico, Zinedine Zidane, Michel Platini and Brazilian women's legend Marta, players who all adhered to a key qualifying rule: they had actually worn the No.10 shirt throughout their careers. But there are significant others inside, too, such as Ferenc Puskas, Ronaldinho, Roberto Baggio, Gunter Netzer and Glenn Hoddle.

The one glaring omission – as Bollen admits himself – is Johan Cruyff, who famously wore No.14 for most of his career having plucked that shirt from the Ajax kit hamper and having turned in a good performance, stuck with the jersey. 

When Platini was attracting rave reviews for his performances in the St Etienne midfield in 1982, Gianni Agnelli, the then Juventus owner, flew to France with the intention of signing him. Agnelli wanted to watch Platini play in a match before parting with the money that would be required to sign one of Europe's hottest properties but it was not so much his performance over the 90 minutes that convinced the Italian rather than Platini's dedication on the training ground – where Agnelli watched him spend hours perfecting free-kicks.

Bollen notes that Platini's diligence chimes with that of others, too.

“Even when Zidane was playing for France he would be out after training, placing cones, and dribbling the ball. Even as the best player in the world and at Real Madrid, he shocked people by working on the basics, he constantly worked on his game.”

And he sees a similarity with another No.10 famous for his free-kick taking ability, one who grew up thousands of miles away in Brazil.

“When Zico was a kid he famously placed his tracksuit top over the crossbar and wouldn’t go home until he hit it ten times in a row. He could be there for hours. As a player and coach he compared the technique of passing, heading, and free kicks to muscle memory, a mechanical thing, like brushing your teeth.”

The Herald:

Tragedy at a young age shaped the lives of Eusebio and Luka Modric, two further entrants in Bollen's book. The Portugal legend lost his father at the age of eight to tetanus and his mother, Elisa, raised the family on her own. Modric, meanwhile, was a young boy when his grandfather – also Luka – was executed by Serbian vigilantes in the mountains near his home during the war in Yugoslavia. Modric Jr, then just 10, was present when his grandfather's bloodied body was dragged back to his home by his father – a harrowing image which he later recounted in his autobiography. When the family moved to a safer location – a hotel in Zadar – he trained in the car park often minutes before the air raid sirens would go off.

Bollen attributes Modric's ice-cool temperament under pressure to this unconventional upbringing saying: “How frightened are you going to be walking on to a football pitch when you've had bombs falling on you? It's a walk in the park. It gives you a different mentality.”

Baggio was another who overcame adversity – but later in life. The Divine Ponytail played in pain throughout much of his professional career due to cruciate ligament problems in his knees, a matter which was hardly helped by him being allergic to painkillers.

But if there is one characteristic, above all, that all of these greats shared it was mettle.

“All the players in the book had so much weight on their shoulders for club and country yet they all had the mental strength to deliver in the critical moments, when it mattered. Those who wear the 10, Messi, Maradona and Zidane despite their wonderful skill also have a hunger and desire, are capable of fighting when it gets tough, and dragging their side to greatness. [But] I think Pele is the best ever because he transcended his sport, like Muhammad Ali.”

The Number Ten: More Than a Number, More Than a Shirt, published by Pitch Publishing is out now, priced £16.99.