The tournament is being played as a joint ATP and WTA Tour on clay for the first time, with men's play set to start on Sunday. It was previously a men's hard court event.
Eighth-seeded Nadia Petrova also advanced after Iveta Benesova of the Czech Republic retired when trailing 6-0, 2-1, while 15th-seeded Zheng Jie of China ousted Russia's Maria Kirilenko 6-4, 6-4.
No. 11 Marion Bartoli of France was eliminated, however, losing 7-6 (2), 6-2 to Aleksandra Wozniak of Canada.
Also advancing were Russian duo Alisa Kleybanova, Anna Chakvetadze, along with Virginie Razzano of France.
Serena and Venus Williams and top-ranked Dinara Safina are also in the tournament, but were not in action Saturday.
Rafael Nadal is the top seed on the men's side, but said he was not impressed by the blue-colored clay used for the event.
"The clay tour has its history,'' he said. "The surface is red, not blue. And tennis is not just show business. History and tradition need to be valued also.''
The state-of-the-art stadium, designed by French architect Dominique Perrault, boasts retractable roofs over its three main arenas, including a center court holding 12,500 spectators.
The site was inspected by the International Olympic Committee this week as a key venue in Madrid's 2016 Olympics bid.
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