Defending champion Roger Federer beat Tomas Berdych to reach the Australian Open semifinals.
MELBOURNE, Australia (AP) Roger Federer accounted for a long-time rival to set up a semifinal against Next Gen champion Hyeon Chung at the Australian Open.
Defending champion Federer's 7-6, 6-3, 6-4 win over Tomas Berdych on Wednesday night extended his winning streak to 14 in Australian Open quarterfinals and to nine in that personal duel. The 19-time major winner leads that head-to-head contest 20-6, including all five meetings at Melbourne Park.
The 36-year-old Swiss star overcame a shaky start, dropping his opening service game and uncharacteristically challenging the chair umpire because of a technological fault.
''I had to get a bit lucky. A bit angry. A bit frustrated maybe at the umpire,'' Federer said. ''Anyway, glad to get out of that first set. It was key to the match.
''That first set could have gone either way. He deserved it, actually. I stole that one a little bit.''
Chung became the first Korean to make a Grand Slam tennis semifinal when he beat No. 97-ranked Tennys Sandgren 6-4, 7-6 (5), 6-3 in the afternoon match on Rod Laver Arena.
The 21-year-old Chung hadn't let up when upsetting No. 4 Alexander Zverev or six-time Australian Open champion Novak Djokovic en route to the quarterfinals, but he let his guard down in the last game and needed six match points and to fend off two break points to hold off Sandgren.
''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,'' he 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 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.
''I think all the people is watching Australian Open now because we make history in Korea,'' he said.
The No. 58-ranked Chung is the lowest-ranked man to reach the Australian Open semifinals since Marat Safin in 2004. He's also the youngest to reach the last four at a major since Marin Cilic did it here in 2010.
With Chung already through, and Kyle Edmund playing No. 6 Cilic in the other half of the draw, it's the first time since 1999 that multiple unseeded players have reached the Australian Open semifinals.
Federer said he has been impressed with the way the two unseeded players have progressed, particularly Chung's run.
''To beat Novak on this court is particularly difficult. ... He's incredibly impressive in his movement, reminds me obviously a lot of Novak,'' Federer said. ''He's clearly got nothing to lose. I will tell myself the same and we'll see what happens.''
Chung's big wins over Zverev and Djokovic have drawn extra attention to a player who last November won the inaugural Next Gen ATP Finals title.
He was too consistent for Sandgren, a 26-year-old American who had never won a match at a Grand Slam tournament or beaten a top 10 player until last week.
Sandgren's unexpected surge to the quarterfinals - he beat 2014 champion Stan Wawrinka and No. 5 Dominic Thiem en route to the quarterfinals - was overshadowed by heavy scrutiny of his Twitter account and his follows and retweets of far-right activists.
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 recovered from an early break to win nine straight games in a 6-3, 6-2 win over No. 6 Karolina Pliskova and set up a semifinal match Thursday against 2016 champion Angelique Kerber, who routed U.S. Open finalist Madison Keys 6-1, 6-2.
In the other semifinal, No. 2 Caroline Wozniacki will play 22-year-old Elise Mertens.
Kerber has been the only Grand Slam singles champion in the women's draw since her third-round win over Maria Sharapova. Two-time French Open finalist Halep has had a tougher road - having to save match points in a third-round win over Lauren Davis that finished 15-13 in the third - to reach the semifinals at Melbourne Park for the first time.
Kerber has had no serious distractions on a 14-match winning streak, and is hoping to emulate her breakout year in 2016.
She won the Australian and U.S. Open titles two years ago and reached the No. 1 ranking, but slipped into the 20s last year. She didn't win a title between the 2016 U.S. Open and the Sydney International earlier this month.
''I am just trying to find the feeling back that I had, like 2016, and just enjoying my time,'' Kerber said.