Former champion Maria Sharapova and last year's runner-up Vera Zvonareva were opening-day winners, while Wimbledon champion Petra Kvitova came up a first-round upset victim Monday at the 2011 U.S. Open.
World No. 1 and defending champion Caroline Wozniacki highlighted Tuesday's second-round winners, while U.S. Open champion Samantha Stosur was an upset victim at the $2.05 million Pan Pacific Open tennis event.
Top-seeded Roberta Vinci eased into the quarterfinals, while second-seeded Russian Maria Kirilenko and defending champion Anabel Medina Garrigues were second-round losers Wednesday at the $220,000 Estoril Open tennis event.
Slovakia's Dominika Cibulkova advanced, but former Cincinnati champion Jelena Jankovic and ex-French Open titlist Francesca Schiavone were opening-round upset victims Monday at the WTA's $2.168 million Western & Southern Open.
After enjoying an opening-round bye, former world No. 1 and reigning Australian Open champion Victoria Azarenka was a second- round winner Tuesday at the $2.369 million Western & Southern Open tennis event.