Danish top seed Caroline Wozniacki was upset in the second round of the WTA Stanford hardcourt tournament, falling to 60th-ranked Varvara Lepchenko 6-4, 6-2.

The Uzbek-born American took only 92 minutes to eliminate the world number five and book a quarter-final date with Germany's 63rd-ranked Mona Barthel. Wozniacki received a bye in the first round.

Polish second seed Agnieszka Radwanska outlasted Japan's Misaki Doi 1-6, 6-2, 6-0 to reach a last-eight matchup against German fifth seed Angelique Kerber, who downed Croatian Ana Konjuh 6-4, 6-3.

Czech fourth seed Karolina Pliskova, who advanced 7-5, 6-2 over Japan's Kimiko Date-Krumm, will meet Croatian Ajla Tomljanovic in the quarter-finals.

The other quarter-final will be between American Alison Riske and Ukraine's Elina Svitolina.

The event lost its star headliner when world number one Serena Williams withdrew. The American is going for her fifth consecutive Grand Slam singles title and the 22nd of her career at the US Open next month in New York.
Source: AFP