Australian Open: Naomi Osaka up for a Coco crunch

Fifteen-year-old prodigy Coco Gauff set up an Australian Open blockbuster with defending champion Naomi Osaka today.

American teenager Gauff, showing a tenacity which is becoming her trademark, clawed her way back from a set down to beat the experienced Sorana Cirstea 4-6, 6-3, 7-5.

Gauff, who bellowed and pumped her fists as she completed her victory, said her "will to win" had got her through the tough second-round match at a windswept Melbourne Park.

"My parents always told me you can always come back -- no matter what the score is," said Gauff, who beat seven-time Grand Slam champion Venus Williams in round one.

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Gauff also beat Williams on her Grand Slam debut last year at Wimbledon, and in another quirk, she faced Osaka in the US Open third round, going down meekly in straight sets.

Japan's Osaka, 22, beat China's Zheng Saisai 6-2, 6-4 but briefly lost her cool mid-match, hurling and kicking her racquet when she gave up a break in the second set.

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"I was thinking that I really don't want to play a third set this time," explained Osaka, who is defending a Grand Slam title for the second time.

Former world number one Wozniacki, playing her final tournament before retiring, came from behind in both sets for a 7-5, 7-5 win over Dayana Yastremska of Ukraine.

Serena Williams shouted at the top of her voice during a testing second set against 70th-ranked Tamara Zidansek, before seeing off break points to win 6-2, 6-3.

"She was a really good fighter -- she did not just let me win," said Williams, who can equal Margaret Court's record of 24 Grand Slams if she lifts the trophy.

Serena Williams said that she was "nowhere near" as good as 15-year-old Coco Gauff when she was that ageas the American great.

Serena Williams said that she was "nowhere near" as good as 15-year-old Coco Gauff when she was that age as the American great reached the Australian Open third round Wednesday despite being far from her best.

The former world number one and Gauff -- touted as a possible long-term successor to Williams at the top of women's tennis -- spent some of the off-season together.