Just saying, Nadal had a much better American hardcourt season than Djokovic last year (Nadal won the US Open event series and Gold Medal), and this year Nadal will only focus on the US Open because he knows its the most important tournament of the year for him. So don't expect Nadal to sacrifice his stamina this time for the non-slams. Most importantly, no Olympics. Djokovic ran out of gas last year at the US Open, and that was with a lighter schedule than Nadal, so I'd be worried about Djokovic burning out.
no doubt nadal's focus will be on the Open, though, what i'm saying is, you don't want to skip events and let dangerous rivals such as murray or djokovic back in.
after winning his first grand slam, mid season last year was a major slump for djokovic, yet still he managed to break nadal's streak in cincinnati. this year i can't see him falling before the final in new york.