Originally Posted by single_handed_champion
Nadal has had a FAR longer career than Isner already. In fact I would say that given Isner is already 27 and has not done anything of note at the Slams, his window is narrowing.
Isner took up tennis late and is therefore a late developer.
You have to give a lot of credit to someone having that disadvantage going into a very difficult and competitive sport.
He's still reached a very high level.