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.
That's what I like about Messi. He does all his talking with his feet.