Caroline Wozniacki's first opponent as a grand slam champion and the new world number one will be 16-year-old Anastasia Potapova after the wildcard claimed a surprise win at the St Petersburg Ladies Trophy.
Wozniacki was restored to world number one after beating Simona Halep in the Australian Open final to win her first major.
Next on the horizon for her will be teenager Potapova, the world number 235 stunning Tatjana Maria to earn a 6-2 6-4 victory.
Also through is Alize Cornet, a 6-3 7-5 winner over Mona Barthel, and Katerina Siniakova, who beat Donna Vekic in three sets.
Meanwhile, at the Taiwan Open, second seed Zhang Shuai was beaten 6-2 6-4 by Kateryna Kozlova.
Fifth seed Yulia Putintseva and sixth seed Zarina Diyas both progressed from the first round, as did Monica Niculescu, Duan Ying-ying and Chang Kai-chen.