Highest market value: £105m (d.o.v - August 7 2012)
Current market value: £105m
As if it was in any doubt. Recent reports of €250m Adidas-backed bids for the Argentinian not withstanding, it's clear that Messi is the world's most valuable player.
He's 26-years-old, scores 70-odd goals a season and plays for Barcelona. You're going to need to break the £100m mark to get hold of this guy.