Hyeon Chung is the first Korean to reach the last four of a Grand Slam. On the women's side, Germany's Angelique Kerber Kerber is the only Grand Slam singles champion still in the draw.

Chung Hyeon of South Korea during his Australian Open quarter-final match against Tennys Sandgren of the US, Melbourne, Australia, January 24, 2018.
Chung Hyeon of South Korea during his Australian Open quarter-final match against Tennys Sandgren of the US, Melbourne, Australia, January 24, 2018. (Reuters)

Serving for a spot in the Australian Open semi-finals and with the score at 40-love, Hyeon Chung started thinking how he might celebrate being the first Korean to reach the last four of a Grand Slam.

Not so fast. He hadn't let up when upsetting No 4 Alexander Zverev of Germany or Serbia's six-time Australian Open champion Novak Djokovic en route to the quarterfinals. But he let his guard down for a few points against No 97-ranked Tennys Sandgren of the US.

He missed four match points in the last game and had to fend off two break points, including one in a 31-shot rally dominated by slice backhands, before finally beating Sandgren 6-4, 7-6 (5), 6-3 in Melbourne on Wednesday.

"In last game, I think at 40-love ... if I win one more point, I make history in Korea. I have to think about the ceremony, something," Chung said, explaining how he got slightly ahead of himself. 

"After deuce, break point. I was like, no, nothing to do with ceremony. But just keep playing – keep focused."

Then he fully embraced the moment, joking with Jim Courier in an on-court TV interview, introducing the audience to his parents and his coach, and taking the microphone to speak in Korean to millions of new tennis fans back home.

The world No 58 is the lowest-ranked man to reach the Australian Open semifinals since Marat Safin in 2004. At 21, Chung is also the youngest to reach the last four at a major since Marin Cilic did it, also at the Australian Open, in 2010.

With Chung already through, and Briton Kyle Edmund playing No 6 Marin Cilic of Croatia in the other half of the draw, it's the first time since 1999 that multiple unseeded players have reached the Australian Open semi-finals.

Federer next up for Chung

Chung next faces Swiss defending champion Roger Federer, who eased past Czech Republic's Tomas Berdych  7-6 (7/1), 6-3, 6-4 in his quarter-final. It will be Federer's 14th Australian Open semi-final.

Kerber looking for a second singles title

Angelique Kerber of Germany hits a shot against Madison Keys of the US during their Australian Open quarter-final, Melbourne, Australia, January 24, 2018.
Angelique Kerber of Germany hits a shot against Madison Keys of the US during their Australian Open quarter-final, Melbourne, Australia, January 24, 2018. (Reuters)

Two women who've been to this stage at a Grand Slam before will meet in the last four. One has two major titles, the other still seeks a breakthrough.

Top-ranked Simona Halep of Romania recovered from an early break to win nine straight games in a 6-3, 6-2 win over No 6 Karolina Pliskova of the Czech Republic and set up a semi-final match against 2016 champion Angelique Kerber, who routed US Open finalist Madison Keys 6-1, 6-2.

Germany's Kerber has been the only Grand Slam singles champion in the women's draw since her third-round win over Russian Maria Sharapova.

She has had had no serious distractions on a 14-match winning streak, and is hoping to emulate her breakout year in 2016.

She also won the US Open in 2016 and achieved a No 1 ranking. But she slipped back to the 20s last year. She didn't win a title between the 2016 US Open and the Sydney International earlier this month.

Seeded 21, her first three wins in Melbourne were in straight sets but a fourth-round struggle against No 88 Hsieh Su-wei of Taipei had commentators wondering if Kerber was in 2016, or 2017 form.

She responded with six service breaks against the No 17-seeded Keys, finishing off the match in 51 minutes and improving her record to seven wins in eight matches against the American.

"I am just trying to find the feeling back that I had, like 2016, and just enjoying my time," Kerber said.

Two-time French Open finalist Halep has had a tougher road – having to save match points in a third-round win over American Lauren Davis that finished 15-13 in the third – to reach the semifinals at Melbourne Park for the first time.

Thursday's centre court order of play on Day 11

Mixed doubles – quarterfinal:

Storm Sanders (Australia)/Marc Polmans (Australia) v Maria Jose Martinez Sanchez (Spain)/Marcelo Demoliner (Brazil)

Women's singles – semifinals:

Caroline Wozniacki (Denmark) v Elise Mertens (Belgium)

Simona Halep (Romania) v Angelique Kerber (Germany)

Men's singles – semifinal:

Marin Cilic (Croatia) vs Kyle Edmund (Britain)

Men's doubles – semifinal:

Bob Bryan (US)/Mike Bryan (US) v Juan Sebastian Cabal (Colombia)/Robert Farah (Colombia)

Source: AP