Wawrinka stopped Marcos Baghdatis 6-1, 7-5 without allowing Baghdatis a break opportunity. Wawrinka took 75 percent of the points on serve in the first set and 77 percent in the second.
Wawrinka, now 4-0 versus Baghdatis, also finished off three of his four break chances.
He goes against sixth-seeded Dmitry Tursunov, who capped Thursday's play with a 6-2, 6-4 decision over Pablo Carreno Busta. Tursunov was on the court just 60 minutes as he won 60 percent of the points in the match and was 4-of-5 in break-point conversions.
Also Thursday, unseeded Joao Sousa advanced over Pablo Cuevas 4-6, 7-5, 6-0.
That put Sousa into a quarterfinal pairing against top-seeded David Ferrer while Melzer plays Federico Delbonis in the other match Friday in that half of the draw. Wawrinka draws Tursunov and Benneteau meets Adrian Mannarino in the other quarterfinals.