(Djokovic is doing absolutely nothing different this year tactically. He is simply outlasting Nadal, and everyone else, in the long baseline rallies. So Nadal will defeat Djokovic when Djokovic's stamina level drops, or when Nadal's stamina level rises. Nadal may simply choose maintain his current level and 'wait out' Djokovic and take advantage when there is a slip in stamina level. But at the US Open final, Nadal really lost because Djokovic had a back injury, and it made Djokovic try to end the points very quickly in the 4th set, Djokovic 'went for broke' and the balls went in. Nadal had begun to win the long rallies before that, so Djokovic stopped the long rallies and won with clean winners. Nadal needed to recognize what was going on, and had to attack more, and end the points early too.
However, I noticed in the 2009 Australian Open, Nadal was playing plenty of drop shots, bringing Federer to the net and passing him. Can't remember Nadal playing drop shots against Djokovic. Djokovic is a lot further behind the baseline than Federer, so surely Nadal should use this, and when you consider how many big break points Nadal failed to deliver on vs Djokovic, he would definitely benefit from using the drop shot on those crucial points. And Nadal did tend to use the drop shot on the big points vs Federer, the deuce points and the points when Federer had break points on the Nadal serve. Nadal was frequently down 15-40 in that 2009 AO final)