Washington: Japanese fourth seed Kei Nishikori outlasted American Sam Querrey 6-4, 5-7, 6-4 Wednesday to reach the third round of the ATP and WTA Washington Open.
Nishikori, seeking his sixth career title and third of the year, fired nine aces in advancing after one hour and 52 minutes at the $1.9 million (1.4m euro) hard court tune-up for the US Open.
The 24-year-old Asian star, ranked 11th, next faces Slovakian Lukas Lacko with French sixth seed Richard Gasquet a potential quarter-final foe.
Dominican Victor Estrella Burgos pulled off the biggest upset so far by ousting spanish eighth seed Feliciano Lopez 7-6 (7/5), 6-4.
Also moving on was American Donald Young, who downed France`s Julien Benneteau 6-4, 6-3.
Czech top seed Tomas Berdych, Canadian second seed Milos Raonic and US fifth seed John Isner were set for later matches.
On the women`s side, Japan`s Kurumi Nara was leading 3-6, 6-2, 4-0 when Kazak Zarina Diyas retired with a right elbow injury.
That advanced Nara into a third-round match against France`s Kristina Mladenovic, who followed up ousting Czech top seed Lucie Safarova with a 6-3, 6-4 victory over US qualifier Taylor Townsend.
New Zealand`s Marina Erakovic ousted American Shelby Rogers 6-2, 6-2.