~snip~
Doesn't really matter even if the players try to have themselves in the best form and increase their fitness levels to play at any age. Still, we all know a player with the age of more than 35y old can't have a good performance like a player in 25y old, and nothing can change this, even if the player is in their best form.
That's Why I think instead of using old players the national teams should start focusing on younger players and making them ready for the world cup.
Absolutely, even a superstar in their late thirties is worse than a good player at their early twenties.
It's a sad reality, but that's just how biology works.