Nadal is already the only man ever to win 3 slams on 3 different surfaces in a calendar year. If Nadal accomplishes this AGAIN, that would surely represent the most incredible feat in history. It would be more impressive than 16 slams (though the feat would put him at 13 slams anyway, so he would likely reach 16). The only question is whether it would be more impressive than Laver's double-calendar year grand slam, which came in an era that wasn't as deep as today (I think even Laver would admit this). Either way, another triple-surface-triple would put Nadal ahead of Federer in history.