For me, Djokovic just needs to stick with the tactic. Gives deep returns and plays a lot of short and deep cross-court forehands to Nadal's backhand, and then hit forehand down the line. If Nadal catchs it, then uses backhand or forehand do it again. That is the play works so many times against Nadal. What it does is Nadal will use much more energy in entire match. Much more than Djokovic. Just don't place too much ball to Nadal's forehand side.
In other hand, Nadal needs to give 1st serve and high 1st serve percentage. And he has chance to use this resume to bring energy back. But so does to Djokovic.