China's tennis star Zheng Qinwen hit a season-high 23 aces to outplay former world number 1 Naomi Osaka of Japan in the first round of the Women's Tennis Association (WTA) 500 Berlin Open on Tuesday.

The world number 8 took 130 minutes to defeat Osaka in three sets, 6-4, 3-6, 6-3 improving her head-to-head record to 2-1.

The victory was Zheng's second of the season over Osaka after beating the Japanese on clay last month at the WTA Italian Open in Rome.

"I've played against her already on all different surfaces—hard, clay, and now grass court," Zheng said on the court. "She's a tough opponent in the first round. I'm happy that I gave my best today and got my first win at this tournament in three years."

"The last two years, when I came on grass, I was a little bit lost," she added.

Zheng's 23 aces were the most hit in a WTA Tour-level match this season, besting the previous best of 19 by Karolina Pliskova against Anna Kalinskaya in Doha.