Roy Keane was one of the most aerobically fit footballers in the premiership (not the best but certainly fastest league in the world) in his prime in the mid to late 90's. he was arguably the best box to box midfielder in the world. he was recorded as clocking between 6-8 miles per game. that's 90 minutes with a 15 break for half time. in comparison to a sunday runner, thats not good at all. (however, its a very diificult comparison to make as the sports are so different). footballers as a rule aren't that aerobically fit. you'll find that when in hard pre season training, runs of 8 miles at 7 minute mile pace are about as long and tough as any of them will manage.
With regard to how fast some of them are, i find it hilarious when certain times are bandied about. someone said rommedahl had clocked 10.2 for 100?! now, ive seen him play in the flesh and theres not a hope of the guy breaking 11 seconds for the hundred. someone like aaron lennon (young spurs winger) could probably clock a decent 60 metre time but would really struggle over 100.
On the opposite side of the coin, i remember former brittish 100 metre champion darren braithwaite giving up track in the mid 90's to try and make it as a footballer. he was a low 10 second sprinter. he's never been heard of on the football pitch.
horses for courses etc etc