Sixth seed Zheng Qinwen of China beat Japan's Hibino Nao 5-7, 6-2, 6-2, advancing to the round of 16 in the Women's Tennis Association (WTA) 1000 event, Dubai Duty Free Tennis Championships, on Tuesday.

Zheng, who had recently reached the final of the Australian Open, was in poor condition in the first set and fell behind after consecutive mistakes. She also took a medical timeout during the match.

In the next two sets, Zheng gradually found her own rhythm and eventually secured a comeback win.

In the round of 16, Zheng will face Russia's Anastasia Potapova. The two have had three previous encounters, with Zheng having two wins and one loss.

Reigning Australian Open champion Aryna Sabalenka of Belarus suffered an opening round upset at the hands of Donna Vekic of Croatia, going down 6-7 (5/7), 6-3, 6-0 on Tuesday.

Contesting her first match since her successful title defense at Melbourne Park, Sabalenka blew a 7-6, 2-0 lead to succumb to her Croatian opponent in two hours and 22 minutes.

The 31st-ranked Vekic was aggressive throughout the match, entering her next clash with big-hitting Romanian Sorana Cirstea searching for the first WTA 1000 quarterfinal of her career.

"At all times I didn't give up. I didn't stop believing that I can win. I just kept fighting," said Vekic.

The Dubai Duty Free Tennis Championships, a WTA 1000 event, is being held from February 18 to 24 in Dubai, United Arab Emirates.

(With input from agencies)