Injured world number four Elina Svitolina withdrew and China's eighth seed Zhang Shuai was bundled out of the Hong Kong Open on Thursday -- the latest blows to an event marred by several pre-tournament pullouts.
The top seed Svitolina's withdrawal means her second-round opponent, American world number 114 Nicole Gibbs, received a walkover into the quarter-finals where she will play compatriot Jennifer Brady on Friday.
Big-hitting Brady, ranked 70, easily overcame an out-of-sorts Zhang 6-3, 6-4 in just over an hour.
Brady smacked down seven aces to overpower the world number 31, whose inconsistent serve was broken three times in the second set alone.
"I started strongly with the first break and was aggressive," said Brady.
"My strengths are my serve, my forehand and my athleticism. I can play from every part of the court. I knew she would come back aggressively in the second set so I'm happy with the win."
It left Wang Qiang as the sole Chinese representative in the draw after she breezed past Thailand's Luksika Kumkhum 6-4, 6-4.
Wang will face former US Open champion Sam Stosur of Australia on Friday for a place in the semi-finals.
Ukraine's Svitolina, who is due to play this month's WTA Finals in Singapore, has been carrying a right groin strain which was heavily strapped as she laboured to a first-round victory over Kazakhstan's Zarina Diyas on Tuesday.
- Seeds tumble -
Svitolina told AFP that she sustained the injury during her mammoth 3hr 21min quarter-final defeat in Beijing last week to the eventual champion there, Caroline Garcia.
"I picked up the injury a little bit in Beijing," she said. "It's the groin. All the time when I go for wide shots or stretch I feel it.
"I will probably do some scans now to see how it is, because you know I have Singapore. It's a tough decision because I really wanted to play here."
Svitolina and Zhang's exits are the latest to affect the tournament, which was rocked before it started by the pullouts of three big names.
US Open champion Sloane Stephens, British world number 10 Johanna Konta and France's 13th-ranked Kristina Mladenovic all withdrew with injuries.
Of the star players that did show up at Victoria Park, number two seed Venus Williams was sent packing in her second-round match in straight sets on Wednesday by Japanese teen sensation Naomi Osaka.
And she was swiftly followed by fourth seed Agnieszka Radwanska of Poland, beaten in three sets by Stosur.
It leaves in-form defending champion and world number six Caroline Wozniacki as the highest-ranked player remaining and odds-on favourite to retain her crown.
Wozniacki, who won in Tokyo just two weeks ago, faces little-known Australian Lizette Cabrera, the world number 155, for a place in the quarter-finals later on Thursday.
Svitolina has been enjoying the best season of her career, winning five times on the WTA Tour in Taipei, Dubai, Istanbul, Rome and Toronto while breaking into the top 10 for the first time and hitting a career-high ranking of three.
The Ukrainian now has just 10 days to recover her fitness before the top eight-ranked players battle it out in the season-ending WTA Tour finals.