Fast HC - 2010/2013 US Open. Nuff said.
Grass - 2008 Queen's + Nadal's 2007/2008/2010 runs top whatever
runs Djokovic had against 50-year old Federer.
I have to make some points because this is plain exaggeration based on poor arguments:
1)Queen's 2008 match should indicate the exact oposite. The peakest version of Nadal needed a lot of mental
toughness to beat that Djoker(down 4-1 in the 1st set,down in the TB,down 5-4 in the 2nd).
There are enough matches where Djoker played at a similar level or even better(Wimby11&14 finals,13 semi and Most of his 15 run),suggesting he
would do just well against any Nadal.
2)Beating prime Fed in Wimby is an indirect way of comparing them.
Nadal is a perfect match-up while Djokovic has a bad match-up(as
proved in 2011 when out of prime Fed challenged Djokovic more than prime Nadal).
3)Their peak runs in US Open(2010&2011) are of similar level.
As a proof,they won mirror matches.
4)Using the US13 final as argument is BS. Out of 6 finals Djoker played their that was by far the worst.Peak Nadal vs. garbage Djoker proves that Nadal is better,just as much as 2015 Nadal got demolished time and time again,thus being a worse player than Novak.
You could make a direct comparison with US Open 2015 or 2007 for this matter,which were hardly any worse.
5)Out of all US Opens since 2007 Djokovic would be favoured everytime apart from 10/13,it is simply that they never had the chance to meet,due to the draw or Nadal losing early.