MELBOURNE, Australia - Yesterday, Marta Kostyuk became the first 15-year-old to successfully come through Grand Slam qualifying in 13 years. Today, the World No.521 backed it up with an even more spectacular achievement as she dismissed No.25 seed Peng Shuai 6-2, 6-2 in just 57 minutes - becoming the youngest player to win a main draw match in Melbourne since Martina Hingis in 1996.

Last year's girls' champion isn't short of self-belief, as her press interview after qualifying revealed, and she showed no fear as she immediately broke her more experienced opponent to 15 to start the match. "I was trying to move her," Kostyuk told reporters afterwards. "I knew exactly to play against her and I did that, I'm happy about that."

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Peng had entered the match with no singles match practice this year, having withdrawn from last week's Sydney International due to a right knee injury - and the Chinese No.1's movement was visibly hampered, particularly in the second set.

Kostyuk, too, battled physical issues, having spent over six hours on court in total across three three-set qualifying rounds - played both outdoors and indoors due to rain - and the Ukrainian took a medical time-out while leading 3-2 in the first set.

A mammoth sixth game would prove crucial; though Peng battled valiantly, it was Kostyuk who converted her fifth break point to move into a dominant 5-2 lead.

Marta Kostyuk hugs a member of her team following her 6-2, 6-2 defeat of Peng Shuai at the 2018 Australian Open (Getty)

The teenager betrayed no signs of inexperience as she closed out the set on her first set point - nor as she began upping the ante even further in the second set, breaking the World No.27 to love twice and striking 17 winners as she leapt out to a 5-1 lead. A struggling Peng held on for one more service game, but was unable to prevent Kostyuk sealing a historic win with an ace on her first match point.

At 15 years and 6 months old, Kostyuk had been the youngest player to qualify for a Slam since Sesil Karatantcheva at the 2005 Australian Open, at 15 years and 5 months. She is now the youngest player to win a Slam main draw match since Catherine Bellis's upset of Dominika Cibulkova at the 2014 US Open when she was 15 years and 4 months old, and the youngest player to win a round at the Australian Open since Martina Hingis's quarterfinal run at the age of 15 years and 4 months in 1996.

Not that such records faze her. "I'm doing some records every year, every tournament, I don't feel special about this," shrugged Kostyuk. "If I feel something different every time I play and break a record, it'd be too much."

Neither does she shrink from the big stage - quite the opposite, in fact. "I feel like it's another match, I don't think, 'Oh my God, I'm in second round!' It's another tournament and another experience."

Kostyuk, who is managed by Roger Federer's coach Ivan Ljubicic, also spoke at length about the importance of learning from losses. Two weeks ago, she had qualified for the ITF $25,000 tournament in Playford - but lost in the first round to Valentini Grammatikopoulou 7-5, 6-3.

"I had set point and I did some mistakes in that moment, then after the match I was so upset," she recalled. "Like, I don't want to go to Australia. I will come and I will lose first round in qualies. Oh! Why am I coming here?"

Forcing herself to be patient paid off. "It was like, calm down, that's why we came one tournament before. You learn from mistakes and then you play better. I actually changed a lot here. In one week I managed to change so many things, you cannot imagine."

In Melbourne, everything changed. Kostyuk had told the press after qualifying that returning to the site of her greatest junior triumph made her "feel you can do everything here", and she reiterated the sentiment today. "My body feels that here in Australia, this tournament, I can do actually whatever I want - this I know!" she exclaimed.

She remains unbeaten in Melbourne through six junior wins last year, three qualifying wins last week and now a milestone main draw victory - and will face local wildcard Olivia Rogowska in the second round in a bid to keep that streak going.