The Swiss defeated the world number two 6-1 6-2 in under an hour on Thursday to reach the quarter-finals of the tournament.
"He's an amazing player. He's always tough to beat," Wawrinka told reporters. "Therefore, to beat Andy that easy was a big surprise, for sure.
"I'm playing really good, really strong, really confident with my game."
Wawrinka will face world number eight Jo-Wilfried Tsonga for a place in the semi-finals.