Israeli teenager Shahar Peer came back from a set down to stun sixth seed Ai Sugiyama 5-7 7-6 6-4 in the second round of the Cincinnati Open.
The 18-year-old is now in the the last eight of a WTA tournament for the second time this year.
Swiss top seed Patty Schnyder survived a slow start to defeat Japan's Aiko Nakamura 4-6 6-1 6-3.
Fourth seed Daniela Hantuchova of Slovakia overcame American Chanda Rubin 6-2 7-5.
South Korea's Cho Yoon-Jeong beat Russia's Tatiana Panova 6-7 6-2 6-2.