Yes, Melzer played very well. His passing shots were particularly effective today.
Obviosly Kei lacked preparations (he resumed practiting on court on Saturday) and he was a bit more erratic than usual.
He didn't show any signs he was in pains, but to me he lookes like he wasn't hitting his FH as sharply and hard as usual (probably to avoid the pains to recur?).
Hopefully this loss is a blessing in disguie so that he doesn't push hard while being less than 100%. He had no point to defend at AO anyway.
Good luck in San Jose, Kei!