Barca had a god like teenager who played 72 games in one season for club and country... Since that season he has missed 40% of the games with injury...

Barca had a god like teenager who play 90% of the minutes for club and country. He recently tore in ACL and meniscus, in a low priority international match which nearly all other players were rotated.

The difference is that clubs cannot sign and register new players outside of the transfer window.

If the squad is riddled with injuries, the club will have to work with what they have until the transfer window reopens. In short, their choice and ability to rotate players are restricted to multiple constrains such as injuries, timing, money etc

The NT has none of these constrains (for the international break). They can call up whichever best and fit squad available. If they feel like player A is gassed or not in a good shape, they can easily call up player B before the break starts. They don’t have to sign player B for X amount of money, they just need to add him to the call up list. In short, NT can rotate players easier.

Also disregard how their club probably goes to the USA, back to England and finish in East-Asia in preseason, playing up to 8 full games in preseason.