The ATP and WTA is as different as night and day. You just can't spend the amount of time out of the game he did and start winning slams again, especially at his age and the fact that he has to start playing with a reduced schedule. Look how long it took Delpo to come back and he was never the same player again, even at his young age. Nadal needs to play many events to stay at the top as he is a confidence player and he just can't afford that anymore. He really is done this time. At most he can win one more FO as far as slams go. But I think there is a high possibility Djokovic wins the FO next year.
Delpo needed a year to re-enter the Top-10 -- not THAT long considering he was ranked as low as #485 in January 2011.
Why do you all make it look like Nadal was out of Top-100 already and bound to draw Fed/Djoke/Muzza etc. in 1R/2Rs in his comeback? He's still Top-4, he's protected by his high ranking and will do just fine. Granted, it's unlikely he wins AO or IW/Miami right away but once he steps on clay court he'll be the overwhelming favorite again.