The essential question that has been asked of Roger for the best few years holds true for Rafa if he is to eventually become #1: Can (Roger/Rafa) maintain his unbelievably high level of play for the next x months/years? Realistically, I don't think he'll fall off too much, but I think it's just a matter of time before Novak is #2. And I see the latter as the person who eventually supplants Roger's reign in the top spot.