For Mathieu, who is ranked 42nd, is the second win of the season over the slumping South American world number 6 and his fourth of 2007 against a Top 10 opponent. His win over Gonzalez was played in steady drizzle, which later turned to rain and wiped out several matches at the Estadio Nacional.

"You have to be focussed and move well. It's good to be able to beat a guy in the Top ten, it gives you confidence.", said Mathieu.

In women's play, the top two seeds moved through without difficulty. Number 1 Marion Bartoli of France hammered 330th-ranked Neuza Silva or Portugal 6-2, 6-1; second-seeded Italian Francesca Schiavone beat Croatian Ivana Lisjak 6-1, 7-5. Caroline Wozniacki, who won junior Wimbledon last summer, beat German fourth seed Martina Muller 6-4, 6-0.

Italy's 2006 semi-finalist Flavia Pennetta, seeded eighth, defeated Arantxa Parra Santonja of Spain 6-3, 6-1.

Argentine Gisela Dulko followed up Sunday's first career title from Budapest with an opening win, ousting Julia Schruff of Germany 6-1, 1-6, 6-1