God bless Marcelo.
well, on second thought lendl also got to no. 1 without any GS but then of course he won quite a few.
there are probly players who have got to number 1 without holding GS in their countable rankings too, even though they won GS before.
in this era, i don't think that would be possible given that the trend seems to be that one player wins 2/3 GS a season.