Mathieu, who was injured throughout 2011, earned the key points with the third-seeded Wawrinka converting just two of nine break chances in the second-round match.

A former top-20 player, Mathieu is ranked No. 172 after dropping into the high 700s.

Thomaz Bellucci of Brazil downed fourth-seeded Mikhail Youzhny of Russia 4-6, 6-2, 6-4, and fifth-seeded Feliciano Lopez of Spain rallied to beat Czech Jan Hajek, 6-7 (3), 6-1, 6-4.

Latvia's Ernests Gulbis saved 15 of 17 break points to edge Benoit Paire of France 5-7, 7-6 (3), 6-4.

In the first round, seventh-seeded Colombian Santiago Giraldo beat Swiss wild card Henri Laaksonen 6-2, 6-2.