He played a very bad match against Wawrinka this year.
Chances are he will win it, but also likely he won't. It depends on how he deals with the pressure and what Nadal can do next year.
You don't have faith in Wawrinka this time again?
Or you want to acknowledge that his performance was once in a lifetime?
Either way, for Novak it depends on those 2 factors I feel too.
Something tells me it is so unpredictable now... maybe he should release the pressure to skip more events before RG, or just learn how to finish matches when he has the upper hand (like the Murray SF this year).