One advantage for Nole is that he is still near the top of his game at #2 in the world, many of the better clay court players are older than he is, and there are very few who are near his level on clay as he generally has been the last few years.
One disadvantage is that the current #1 player is Rafael Nadal, the Clay King of this generation and perhaps all time.
So I suppose the real question is who will decline the fastest from this point forward, especially on clay, Nadal or Djokovic?
Some say Nadal has already declined on clay. But he was at such a high level to start with, one would think he has some room to fall.
Novak may have to contend with some of those that still have an excellent game on clay, but there aren't many. One doesn't see many young rising stars on clay at this point either.
I would agree that he has an excellent chance to complete his career slam, especially if Nadal were to fail. But that's the big if. On the other hand, if Soderling could beat Nadal once, something like that could happen again.
Respectfully,
masterclass