It is his silence which defenders find most disconcerting. If they are being torn inside and out by a player of outrageous talent then they generally expect some surreptitious sledging, but you don't get a word from Lionel Messi.
Few are better equipped to explain the giddying experience of marking him than Asier del Horno, who was slaughtered then sent off on the night Messi did for Chelsea at Stamford Bridge in February 2006 and the lack of provocation is the part he still remembers.
"He doesn't say anything," says the 30-year-old, whose winding road since leaving west London has taken him to Levante. "There are many provocations in football between defenders and forwards, but that's not his style. Messi doesn't provoke."
That's always been a significant part of the player they call 'The Flea' and whom Cesc Fabregas says the Barcelona youth squad thought was 'mute' until a reserves tournament in Italy in which "thanks to PlayStation and the (camaraderie of the) trip we discovered he knew how to talk."
There wasn't much chat, for instance, before he undid Manchester United in the Champions League final of two years ago. Nothing at all, in fact, for 35 minutes and suddenly there was Messi; first drifting from the right to operate as the dummy centre-forward which Alex Ferguson admitted forced his central defenders out of position, then ascending to the Roman heavens to head the goal that clinched the final.
The image of Edwin van der Sar, open-mouthed and transfixed, is one of the most iconic of that night.
But United are not the only ones who didn't detect Messi. The remarkable story of how Barcelona captured -- and almost immediately lost -- the talents of the 13-year-old boy from Rosario, on Argentina's Parana River, forms part of an engaging new study of the player by the Italian journalist Luca Caioli.
The scouting systems of football's world powers would like to believe that they now have the networks to scout players for themselves. But Caioli reveals how Martin Montero and Fabian Soldini, from a company established in Rosario to buy and sell players, calmly walked up to the then Messi home -- 525, Estado de Israel -- and, after a conversation with Messi's father Jorge, set the wheels in motion.
Their Nou Camp contact was a Barcelona shareholder, who approached Carles Rexach, the club's then technical director.
The boy arrived in Catalunya on September 17, 2000, then had to hang around until October 3 because Rexach was busy out in Beijing, watching Spain in the Olympics.
It was a long walk around the training pitch when Rexach finally returned to watch Messi play. "By the time I sat down on the bench I had made my decision," Rexach tells Caioli.
The book charts the Messi family's subsequent struggle to tie Barcelona down to a contract. The Barcelona board didn't trust Rexach's judgement that the club should take on the responsibility for a 13-year-old and his entire family and in December, at a meeting with the family's representatives at a restaurant in Barcelona's Montjuic district, Rexach grabbed a napkin and wrote words to the effect that the club promised to buy the boy.
They signed an individual who, Caioli's work makes clear, inherits his bashfulness and his footballing ability from his father, who was a steel works executive before packing up his life in Argentina to accompany Messi.
The entire family initially did, though Messi's mother Celia returned to Argentina when the player's youngest sister Maria Sol did not settle.
It was arguably the player's maternal grandmother, also Celia, who did most to propel him into football, by marching him into training sessions in Rosario and insisting they let little Lionel play. "They were afraid he'd get trodden on," his mother tells Caioli. "But my mother wasn't."
The growth hormone treatment which was such a significant part of Messi's childhood was an important factor in his move to Europe. The Argentine clinician who treated him, Dr Diego Schwarzstein discovered a rare deficiency -- found in one in 20 million, he estimates -- and prescribed one subcutaneous injection a day for a period of three to six years, depending on his development.
The cost of treatment was 600,000 Argentine pesos (€104,500) a year. Schwarzstein tells Caioli the treatment was available for free in Argentina, but Jorge Messi says state benefits covering the treatment stopped and that financial help towards the costs from Newell's Old Boys club, which Messi joined, was also starting to dry up.
"We went so many times to ask for the money, that in the end my wife said to me: 'I'm not going to ask any more'," Messi Snr relates. "I think (Newell's) didn't realise the value of what was in front of them," adds Adrian Coria, Newell's youth-team coach then.
Messi's final, though premature departure on an Aerolineas Argentinas jet forms part of Messi's sometimes difficult relationship with his own country and the portenos (Buenos Aires locals) who expect their nation's stars to play for one of the city's clubs before they leave.
He rejected Argentina's overtures to play international youth football for a while and the shyness meant he hardly spoke to team-mates when he finally joined their ranks for the 2005 U-20 World Cup.
His sense of nationhood is strong though, as Caioli's interview with him for the book reveals in subtle ways.
His favourite music is the Argentine cumbia; his favourite film the Argentine comedy drama 'El Hijo de la Novia' (Son of the Bride.) It has not always been a smooth ride at Barcelona, either. Caioli relates Messi's drawn out struggle for Spanish citizenship, without which he could not break into league football as the club had filled their quota of non-EU nationals. There have been many injuries too.
The abundance of testimonies to Messi's magnificence reveals what those who have been closest to him consider two prime qualities. Foremost, is the ability to have the ball seemingly glued to his left foot and thus operate at a speed which can make a change of direction almost impossible to contend with.
"Technically speaking, he is one of the few strikers in the world who can drive the ball forward without looking at it," says Roberto Perfumo, the legendary former Argentina defender.
The second is an ability to be unaffected by any occasion. "It doesn't matter if he is playing in front of 10 spectators or 100,000," says former coach Frank Rijkaard. "He is always the same."
Caioli also finds those who challenge the suggestion that Messi is the new Maradona. A persistent theme among them is Messi's need to learn he is "part of a whole, has to share the ball, pass it more quickly," as one commentator puts it.
"Diego sometimes used to put his foot on the accelerator, whereas Messi lives with his pedal to the floor," adds Jorge Valdano, Real Madrid's former director general and another compatriot. Rijkaard's advice to Messi was: "Finish the action: shoot, or cross it, don't keep dribbling."
Ferguson has been telling confidantes for some time now that he has an answer to the boy whose school friends knew him as piqui (the smallest). But the Scotsman will not have forgotten that gravity-defying header, arcing over Van der Sar with Rio Ferdinand rooted to the spot.
Messi doesn't make much noise because it is not a requirement. (© Independent News Service)