Roger Federer is back in a familiar spot -- the last four of the Australian Open.
The tournament's second seed swept past No. 19 Tomas Berdych 7-6 (1), 6-3, 6-4 in the quarterfinals Wednesday. With the win, Federer has reached the semifinals in Melbourne 14 of the past 15 years.
Federer, 36, also became the oldest man to reach the semifinals at Melbourne Park since Ken Rosewall did it in 1977 at age 42. He is the oldest man to advance to the final four at any major since Jimmy Connors at the 1991 US Open at age 39.
Federer will next face Hyeon Chung, who overcame a brief distraction to become the first Korean in the last four of a Grand Slam.
The 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 frustrating 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."
Federer's outburst came when he questioned chair umpire Fergus Murphy about a line-call challenge with Berdych serving for the first set in the ninth game.
After a lengthy delay, Murphy called the control room and confirmed the replay graphic couldn't be displayed on the stadium screen and that the original decision stood. When he added that Federer had no challenges remaining for the set, Federer approached the chair and the crowd cheers intensified.
"You can't steal my challenge," Federer told Murphy. "Do you feel comfortable with this? You're OK with it?"
Seven points later, Federer eventually broke Berdych to get back on serve and then won the tiebreaker.
Federer later said he just wanted an explanation from the chair and that blowing off steam helped his cause.
"I was under pressure. It was definitely very close, the turning point," he said. "I played a great breaker. But coming back from 5-2 in the first set, it was clearly big tonight."
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 for a few points against No. 97-ranked Tennys Sandgren.
He missed four match points in the final 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 at Rod Laver Arena on Wednesday.
"In last game, I think at 40-love, I'm thinking what I had to do in ceremony or something like that," 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.
"I think all the people [are] watching the 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. At 21, Chung is also the youngest to reach the last four at a major since Marin Cilic did it at the 2010 Australian Open.
It will be the first career matchup between Federer, who hasn't dropped a set yet in the tournament, and Chung.
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.
"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."
Until the final game, Chung had been simply 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.
Lleyton Hewitt's return to the Australian Open has come to an end, albeit much later than he was expecting.
Hewitt came out of retirement for this year's tournament to play men's doubles with former Davis Cup teammate Sam Groth, who is playing his final tournament.
The pair won three matches at Melbourne Park, including an upset over the No. 3-seeded team of Jean-Julien Rojer and Horia Tecau, but their luck ran out in the quarterfinals as they fell to Colombia's Juan Sebastian Cabal and Robert Farah 6-4, 7-5.
Afterward, two-time major winner Hewitt said "playing in front of great crowds on big home courts like this is what you really miss" in retirement. Hewitt, 36, played his last singles match at the Australian Open in 2016 and is now Australia's Davis Cup captain.
The 30-year-old Groth's career highlight was a semifinal finish in doubles at the French Open and two doubles quarterfinals at the Australian Open.
Hewitt said of his teammate: "I loved playing Davis Cup with this fella. He wore his heart on his sleeve ... and for me to come out and play alongside him in his last event was pretty special."
The Associated Press contributed to this report.