Fifteen-year-old prodigy Coco Gauff on Wednesday set up an Australian Open blockbuster with defending champion Naomi Osaka, as a pumped-up Serena Williams took another step towards a record-equaling 24th Grand Slam title.
On a day when men's seeds tumbled, Serbia's Novak Djokovic strode into the third round to be joined by Roger Federer, who dismissed Filip Krajinovic 6-1, 6-4, 6-1.
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 screamed 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.
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 racket when she gave up a break in the second set.
"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 No. 1 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 all-time mark of 24 Grand Slams if she lifts the trophy.
- Wind 'massive factor' -
Earlier, Australia's world No. 1 Ashleigh Barty raced through 6-1, 6-4 against Polona Hercog, buoying hopes of a first home winner since 1978.
"It was very different end to end, I think the wind was a massive factor particularly with the new ball," she said.
Djokovic also weathered the breeze -- which followed heavy rain on Monday, and smog from bushfires last week -- to beat Japanese wildcard Tatsuma Ito 6-1, 6-4, 6-2 in 95 minutes.
"They were tough conditions, pretty windy and it was hard to know where the balls were going. My serve helped a lot to get me out of trouble," said the Serb.
Federer was barely detained by Krajinovic, the world number 41, as he moved smoothly through in 92 minutes in the night match on Rod Laver Arena.
In other results, Petra Kvitova, last year's runner-up, came through 7-5, 7-5 against Paula Badosa of Spain, and China's Zhang Shuai ousted American Caty McNally 6-2, 6-4.
Former US Open champion Marin Cilic won a five-setter against French seed Benoit Paire, and one-time semi-finalist Milos Raonic beat Chile's Christian Garin in straights.
Tennys Sandgren, engulfed in controversy over his political views and right-wing links during his run to the 2018 quarter-finals, took the biggest scalp so far when he ousted eighth seed Matteo Berrettini in five sets.
Sandgren's fellow American Tommy Paul also pulled off a five-set upset when he beat Bulgarian 18th seed Grigor Dimitrov 6-4, 7-6 (8/6), 3-6, 6-7 (3/7), 7-6 (10/3).
And Australia's John Millman further trimmed the number of high-ranked players when he ended the campaign of Polish 31st seed Hubert Hurkacz.
But Greek sixth seed Stefanos Tsitsipas was handed a slice of fortune when Philipp Kohlschreiber withdrew injured.
Among eight first-round matches held over from Tuesday, after rain wiped out half of Monday's schedule, Spain's Carla Suarez Navarro, also retiring this year, upset Belarusian 11th seed Aryna Sabalenka in straight sets.
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