He definitely lost his legs. It was very evident after the first set that his movement slowed and he just couldn't pressure Wawrinka at all. Anyone would have been physically affected playing four matches in five days, especially on clay and against the tough opposition he faced (Nadal and Murray).I love this post, still want to make small, yet significant comment.
He lost 10-15% of his leg power, as a result of playing three days in a row. That was the dealbreaker eventually for him. He couldn‘t attack, force errors from Stan or counterpunch as usual.
Would he have been able to rest, he would have tamed that beast that Stan was that day. Incredible task, but doable for the guy, who dismantles shotmakers and ballbashers on a regular basis.