Fernandez was ahead 5-7, 6-2, 5-2 when her Russian opponent was forced to retire due to difficulty breathing after a 2-hour, 44-minute battle in the last WTA 500 tournament of the year.
Fernandez will next face France's Varvara Gracheva, a 6-1, 7-6 (4) winner over Japan's Mai Hontama.
Turkish qualifier Zeynep Sonmez upset seventh seed Magdalena Frech of Poland 1-6, 6-4, 6-3.
Bianca Andreescu of Canada picked up her first win since July with a 7-5, 6-3 victory over Japan's Mei Yamaguchi.
Viktoriya Tomova of Bulgaria knocked out defending champion Veronika Kudermetova of Russia 7-6, 6-3.
Guangzhou Open
Sijia Wei of China rolled to a 6-1, 6-4 upset against sixth-seeded Rebecca Sramkova of Slovakia in opening-round action in China.
The 20-year-old Wei, ranked No. 135 in the world, saved four of five break points in the 75-minute victory and will face either Arantxa Rus of the Netherlands or China's Xiyu Wang in the second round.
Olga Danilovic of Serbia defeated Russia's Erika Andreeva 6-4, 6-4 and Romania's Jaqueline Cristian outlasted Viktorija Golubic of Switzerland 6-4, 2-6, 6-1 in other first-round matches.