Fourth seed Elina Svitolina came from a set down to overcome spirited Czech Katerina Siniakova 4-6, 6-2, 6-1. The Ukrainian is now on a seven-match win streak after winning the lead-up Brisbane International.

She picked up five WTA Tour titles last year, more than any other woman, making her a serious Grand Slam contender. Her next task is tackling 15-year-old sensation Marta Kostyuk, who became the youngest woman to reach the third round since Martina Hingis got to the quarter-finals in 1996.

Kostyuk comfortably beat local wildcard Olivia Rogowska 6-3, 7-5. Her win streak at Melbourne Park is now 11 straight matches after claiming the Australian Open girls' title in 2017 and coming through qualifying this year.

"I heard a lot of times that I'm talented, and I know that," said the confident teen. "But I know that only talent will not help me to play good. So I'm working pretty hard."

Svitolina said she knew little about the youngster and was preparing for a no-holds-barred fight. "She has nothing to lose, so that's why I know she goes just for everything. You know, a little bit like a headless chicken," she said.