MELBOURNE, Australia -- Former Australian Open junior champion Marta Kostyuk, a 15-year-old qualifier from Ukraine, advanced Wednesday to the third round with a 6-3, 7-5 win over Olivia Rogowska, a wild-card entry from Australia.
Kostyuk, who entered the tournament ranked No. 521, had already played six hours on court through three three-set qualifying rounds before beating 25th-seeded Peng Shuai in the first round.
The win over Peng gave Kostyuk the distinction of being the youngest player to win a main-draw match at the Australian Open since Martina Hingis in 1996. The Australian Open is not only her first Grand Slam but also her first main draw at any WTA-level tournament.
Kostyuk is managed by Ivan Ljubicic, who works with Roger Federer, so she gets the benefit of some first-rate analysis.
"Ivan is always helping me ... after every match, he's telling me what's wrong," she said, smiling.
While Kostyuk need only two sets to continue her surprising run, second-seeded Caroline Wozniacki needed a dramatic comeback to stay alive in Melbourne.
Wozniacki came from 5-1 down in the third set and saved two match points to beat Jana Fett 3-6, 6-2, 7-5 in the second round.
Fett is ranked 119th and was making her first appearance in the main singles draw of a Grand Slam tournament.
"That was crazy,'' said Wozniacki, who has reached two Grand Slam finals. "I don't know how I got back into the match. I was like, 'This is my last chance. I have to go in and attack.'
"At 5-1, 40-15, I felt like I was one foot out of the tournament. She served a great serve down the T -- it was just slightly out. I was kind of lucky."
Wozniacki won the next nine points and 24 of the 31 points played from when she first faced match point.
Wozniacki twice broke Fett's service while the Croatian player was serving for the match, including the two match points in the seventh game.
Wozniacki then broke Fett's service in the 11th game, helped by a Fett double-fault on break point and an unforced error by the Croatian that ended a 26-point rally. She then held serve, clinching it on her first match point when Fett netted a backhand, giving her a six-game winning streak to end the match.
Bencic was on a high after beating 2017 finalist Williams on center court in the first round but started flatly on Hisense Arena on Wednesday and lost 6-1, 6-3 to powerful-hitting Thai qualifier Luksika Kumkhum.
The 20-year-old Swiss, who combined with Federer to win the Hopman Cup in the lead-up to the season's first major, saved three match points on her serve before netting a backhand to give No. 124th-ranked Kumkhum a spot in the third round for the first time.
"I tried to reset and focus on the next match," Bencic said. "I think it was also a very tough second round, for me the toughest I could get."
No. 42-ranked Cornet had taken only one set in five previous losses to Goerges, who was on a 15-match winning streak after her opening win at Melbourne Park.
Ukrainian women went 3-for-3 in second-round matches Wednesday afternoon, with Kostyuk and Kateryna Bondarenko also advancing. Svitolina plays Kostyuk next.
Svitolina matched her best showing at the Australian Open, having reached the third round in four of the past five years. She has never advanced beyond the third round, however.
The Ukrainian, who won her 10th career title at the season-opening Brisbane International, was 0-for-6 on break-point chances in the first set but recovered to break Siniakova six times over the rest of the match.
Bondarenko beat No. 15-seeded Anastasia Pavlyuchenkova, a quarterfinalist here last year, 6-2, 6-3 to reach the third round in Australia for the third time.
The 31-year-old Bondarenko broke Pavlyuchenkova's serve four times and dropped her own serve only once to register her 20th career win against a top-20 player.
French Open champion Jelena Ostapenko is through to the third round after beating Duan Yingying 6-3, 3-6, 6-4.
It is the second year in a row that the seventh-seeded Ostapenko has advanced to the third round here after losing in the first round in her first appearance in Australia in 2016.
Ostapenko is playing her first Grand Slam with her new coach, Australian David Taylor.
Information from The Associated Press was used in this report.