Sixth-seeded Wang Qiang of China was leading Svitolina 6-2, 5-2, and serving at 15-30, when their match was suspended until Saturday.
Svitolina entered this week as one of five players still in contention to earn a place in the eight-player WTA Finals in Singapore.
Even if she ends up losing the quarterfinal to Wang, she could still possibly land a berth in the WTA Finals. In order to do that, she would need to play the Moscow tournament next week. She's currently not entered, but could request a main draw wild card.
Fourth-seed Garbine Muguruza is into her first semifinal since thes French Open in June after beating Luksika Kumkhum of Thailand 6-2, 7-5.
Muguruza has played seven tournaments since the French Open and this marks the first time she's strung together three match wins. She's yet to drop a set this week en route to the semifinals.
Zhang Shuai of China knocked out seventh-seed Daria Gavrilova of Australia 6-1, 6-3. Gavrilova was a finalist in Hong Kong last year.
Zhang will play 18-year-old Dayana Yastremska of Ukraine in the semifinals. Yastremska got past Kristina Kucova of Slovakia 7-6 (6), 6-2.
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