Number six seed Madison Keys moved into the quarterfinals of the Japan Open with a straight-sets win over Zhang Shuai in Osaka on Thursday.
Keys, an 18-year-old American, prevailed 6-4, 6-0. He is one of three seeds in the last eight of the WTA International hard-court competition, after Sabine Lisicki pulled out ahead of her clash with Polona Hercog.
It leaves Australia's Samantha Stosur, Canada's Eugenie Bouchard and Keys as the only seeded players remaining, with top two Jelena Jankovic and Lisicki both forced to withdraw with left hip injuries.
Keys had a dominant second-set performance to thank for her progression as she eased past the world number 62 from China.
She got the crucial breakthrough in the ninth game before going on to win the last seven games of the match, taking the second set in just 19 minutes.
Keys will face Zheng Jie in the last eight after Zheng sprung a surprise against number nine seed Kristina Mladenovic to win 6-7 (5-7), 6-2, 6-0.
Despite Zheng securing the first break of the match, Mladenovic held firm and took the first set.
However, Zheng proved a dangerous opponent, surging into a four-game lead in the second before reeling off the last eight games of the match to win through.
Misaki Doi and wild card Kurumi Nara will be Japan's representatives in the quarterfinals after the former edged past compatriot Kimiko Date-Krumm 7-6 (7-3), 6-4.
Both Doi and Date-Krumm broke twice in the first set, with Doi amassing a 5-1 lead in the ensuing tie-break. She then got the crucial break in the ninth game of the second before taking advantage of a second match point in the 10th.
Doi will face Stosur, while Nara takes on Polona Hercog of Slovenia. Bouchard will meet Barbora Zahlavova-Strycova.