That's what he means, just say Matthaus, Brehme, Breitner or God forbid, Beckenbauer become available, how are you going to draft them? If you had Maier in goal and another keeper of another nationality on the bench, you could take Maier off for your sub keeper to free up the German spot and bring in one of those legends.
I know what you mean though, never mind worrying about future subs, just try and win your first round! Like I pointed out earlier though, Goal keeper make little of any impact on these drafts usually.