With all due respect to Thiem; he looked jaded, cramping and tired at times in that USO F vs Sascha (the German absolutely lost a straight setter win in 5 sets). At FO, he struggled big time against Gaston physically (couldn't hit through and anticipate as well); and against Schwartzman he was visibly tired after 4 sets and struggled to successfully hit through the Argentinian throughout the match.
I don't think thiem was exhausted. He was just out of form. He showed some flashes of brilliance here and there that's all. But I am pretty confident he will come back strong and win big titles..