Age27
CountryJapan
Residence Chiba, Japan
Turned Pro2008
2016 Earnings$676,267
Osaka blasted seven aces against Japan's top-ranked player and converted two of five break chances.
In another upset, second-seeded Yanina Wickmayer was beaten by Viktorija Golubic, 6-1, 7-6 (7).
Gibbs topped fellow Stanford standout Zhao, 6-2, 4-6, 6-3, in the first evening match.
In women's action, Kerber eased past Doi, Halep outlasted Keys and Cibulkova shocked Radwanska in a thriller.
The 35-year-old defeated Misaki Doi, 6-4, 6-2.
