Paul-Henri Mathieu gains quarters
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.
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A former top-20 player, Mathieu is ranked No. 172 after dropping into the high 700s.
In the first round, seventh-seeded Colombian Santiago Giraldo beat Swiss wild card Henri Laaksonen 6-2, 6-2.
Copyright 2012 by The Associated Press