Azarenka stunned by Kiwi qualifier

STANFORD, California: New Zealand qualifier Marina Erakovic shocked top seed and defending champion Victoria Azarenka 4-6, 7-5, 6-2 Thursday to reach the quarter-finals of the $721,000 WTA Stanford tournament.

Erakovic, ranked 121st in the world, notched her first victory over a top-20 opponent and reached her second quarter-final of the season.

She has won 24 of her last 28 matches.

Azarenka, ranked fourth in the world, arrived in Stanford for this hard court US Open tune up off a semi-final appearance at Wimbledon.

She had enjoyed the first-round bye given to the top four seeds.

Erakovic next faces eighth-seeded Slovakian Dominika Cibulkova.

In other matches, 13-time Grand Slam champion Serena Williams faced Russian Maria Kirilenko for a place in the quarter-finals.

Williams is unseeded as she tries to rebuild her world ranking, which has tumbled in the wake of an 11-month injury and illness layoff.

The winner of that match will face second-seeded Maria Sharapova in the quarter-finals.

Fourth-seeded Australian Samantha Stosur was due to open her campaign with a second-round clash with Germany's Sabine Lisicki.

Japan's Ayumui Morita booked a quarter-final berth against French third seed Marion Bartoli. Morita defeated qualifier Urszula Radwanska of Poland 4-6, 7-5, 6-1.