In general physical exposure like the one footballers are exposed to usually does that to the body. This is why people with desk-jobs usually, actually, look younger than they are. I don't remember how I learned this but I know that is how the body works. Of course there are exceptions like Pippo, Henrik Larsson and so on but in general the more physical exposure the more you "age". This does however not mean it is unhealthy or that you live shorter or anything else. Apparently it's only the looks that are effected. Sorry for the trivia but I think it's interesting.