|2018 Australian Open|
|Dates: 15-28 January Venue: Melbourne Park|
|Coverage: Watch highlights on BBC Two, the BBC Sport website and app. Live commentary on the best matches on BBC Radio 5 live, 5 live sports extra and online.|
Marta Kostyuk became the youngest player to reach the third round of a Grand Slam since 1997 as the 15-year-old qualifier beat Olivia Rogowska at the Australian Open.
The world number 521 won 6-3 7-5 and plays fourth seed and fellow Ukrainian Elina Svitolina in the last 32.
Kostyuk is the youngest player to reach that stage at a Slam since Mirjana Lucic-Baroni in the 1997 US Open.
She is the youngest in the last 32 at Melbourne since Martina Hingis in 1996.
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Kostyuk, the 2017 Australian Open girls' champion, said: "I was lucky that I played finals on Rod Laver last year. So I kind of knew how is it to play on the big court.
"I was pretty tight in the beginning, but not in the shots; more in the serve."
Kostyuk was given a wildcard into Australian Open qualifying as last year's junior champion, and has now won five matches - including her first at senior level - to reach the third round proper.
She had been entered in the girls' singles again this year but confirmed after Wednesday's match that her junior career was now over, with her WTA ranking projected to rise inside the top 250.
Kostyuk had won about £5,000 in her fledgling career before arriving in Melbourne, but two victories this week have already guaranteed prize money of £82,000.
"I already know a little bit where I'm going to spend this," she said.
"Maybe I will get the presents for my family, first of all, of course. Because I have big family. And then for myself a bit."
Opening play on the main Rod Laver Arena, Svitolina had to come from behind to beat Czech Katerina Siniakova 4-6 6-2 6-1.
Looking ahead to facing her compatriot, Kostyuk said: "I will just enjoy it.
"I think I'm going to play on a big court again, but I will just try to show my best tennis, because I'm pretty sure, like, all my opponents, she will struggle a little bit, and I will try to use this.
"That's what I'm going to do. I know a little bit how Elina is playing, but I still didn't go into the details."
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