No, a better player doesn't necessarily win even if he plays A game, a lesser player with potential actually has a say. There is no question, zero, that Novak is better than Stan. Yet when Stan shows up, usually in big matches, he can play at a level that Novak just cant handle even though we all see that he actually plays well, much above his average. Nick is similarly explosive, perhaps more, and clearly he is wired in a way that he shows up against the best players...…….while often at other time he becomes pathetic when opposition is average. It can't be a coincidence that he is tied with Nadal, and leads Novak and Roger actually got a bit lucky in some matches when it was on Nick's racquet to close those out. I do believe he is confused how he is naturally wired like that, sometimes he is incredible and sometimes he becomes so flat.
With Nick one thing is for sure, you just never know.