Have you not noticed that Nishi's body has not lasted a full fortnight in a slam yet
The defeats you reference have much more to do with the former than nishikori being simply outplayed!
I don't really agree that Nishikori lost because he was injured, but in any case if what you say is true, then it's a lot worse for Nishikori than my diagnosis. His body can't take two weeks of slam punishment? As I noted, he should be at his physical peak right now. If he's getting worn down now, he's doomed in the future.