Because Nadal is getting better on HC, Del Potro sooner or later will be back & of course we have Federer & Djokovic too
Those are all players that can beat Murray, but Murray has proved he can maintain his form through the two weeks required to win a slam. That was my point: "2 weeks, best of 5" tournaments are not off limits to him, as you seem to think. This was a bad loss, but so was his loss to Cilic at the same time last year.
Since he won his first masters title, he's had a positive H2H with all the players you list. It is *possible* for him to beat them. Whether he will is another matter of course.