I think perhaps Djokovic would be easiest to beat. Then again, Djokovic is no joke on HC and he has owned Nadal on HC in their last matches, but this is best of 5, so I think I'll say Nadal is the favorite in that match up.
It's the other way around with Fed. Nadal owns Fed on H2H, but it's pretty even on HC. Fed is playing very well these days. I'd say Fed is the favorite in that match up.
Still, I'll be surprised if Nadal were to meet Djokovic in a potential final. I think he'll meet Federer instead. But sure, it's not unlikely that he'll face off against Djokovic. Djokovic does have a decent shot of beating Federer today, even though he is the underdog. We'll see what happens today first though