Defending champion Aryna Sabalenka set up a tantalising Australian Open semi-final against American teenager Coco Gauff after overpowering Barbora Krejcikova in a straight-set victory.
Sabalenka's 6-2 6-3 win confirmed a repeat of September's thrilling US Open final, in which Gauff came back from a set down to win a first major title.
Gauff, 19, scraped past Ukraine's Marta Kostyuk in three sets in Melbourne.
The American made 51 unforced errors but won 7-6 (8-6) 6-7 (4-7) 6-2.
Belarusian Sabalenka, who claimed her maiden singles Slam triumph on Rod Laver Arena 12 months ago, hit 20 winners and broke Czech 2021 French Open champion Krejcikova's serve six times in a devastating quarter-final display.
That was in sharp contrast to last-four opponent Gauff's victory, with the fourth seed saying she hopes to have "got the bad match out of the way" as she aims to become the first women's player since Naomi Osaka three years ago to win back-to-back majors.
The other two quarter-finals in a women's singles draw blown open by a string of high-profile early exits take place on Wednesday.
One of China's Zheng Qinwen, Russia's Anna Kalinskaya, Ukraine's Dayana Yastremska and Czech Republic's Linda Noskova - none of who have ever played in a Grand Slam semi-final - will meet Gauff or Sabalenka in Saturday's showpiece.
Sabalenka continues to shine
Sabalenka could not have wished for a much smoother Australian Open title defence to this point.
The 25-year-old is yet to drop a set at Melbourne Park this fortnight, conceding just 16 games in five matches on her way to the last four and not losing more than three games in any single set.
She took just 71 minutes to dismiss ninth seed Krejcikova - the longest she has been kept on court at this year's tournament - before she prepares to exact revenge on Gauff.
The second seed was already up a double break in the opening set by the time Krejcikova landed a first blow, momentarily reducing the deficit to 4-2 before a fired-up Sabalenka struck for a third time.
There was little Krejcikova could do to delay Sabalenka as she again trailed 4-1 in the second set, earning one break back before falling to the first of three match points on her serve.
Unbeaten in her last 12 matches in Melbourne, Sabalenka has now reached the semi-finals at her past six Grand Slams, becoming the first player to achieve that feat since Serena Williams made 10 in a row between 2014-17.
Gauff falters but finds a way through
Coco Gauff has reached the Australian Open semi-finals for the first time
Gauff had breezed into the Australian Open last eight with a series of clinical and composed performances but her display against world number 37 Kostyuk - the highest-ranked player she has faced so far - was far from convincing.
Both players looked tight and tense in a match where they made 107 unforced errors in a total of 246 points.
Gauff, who hit just 17 winners in comparison to her 51 unforced errors, fought back from 5-1 down in the first set but failed to serve out the second.
The three-hour contest featured 16 breaks of serve and Gauff took nine of them, including three in the decider, to progress.
"I think it was definitely a 'C' game - I didn't play my best tennis but really proud that I was able to get through the match," said Gauff, who had never previously gone beyond the fourth round in Melbourne.
"Hopefully I got the bad match out of the way and I can play even better."
The teenager has looked a different proposition over the past six months, playing with more confidence and trust in her ability under the guidance of renowned coach Brad Gilbert.
Showing more faith in her previously shaky forehand has been a key factor in her renaissance after a chastening first-round exit at Wimbledon last year, since when Gauff, unbeaten at the start of the 2024 season, has lost only four matches.
But that old failing reappeared - particularly in a second set in which Gauff admitted she became "became a little bit passive" - and she had to dig deep to find a way past Kostyuk.
Kostyuk, 21, was playing in her first major quarter-final and says she is "proud" of a run she hopes will remind people of the ongoing Russian invasion of Ukraine.
"I was texting with some people from [Ukrainian capital city] Kyiv. I said 'How is it? How are you guys?' They said 'Well, we were looking between your score and where the missiles are flying," Kostyuk said.
"It's very exhausting to live in this state. The war is still there. It's not gone."
BBC