Melbourne - Roger Federer resumes his long-time rivalry with Tomas Berdych as giantkillers Chung Hyeon and Tennys Sandgren face off in an Australian Open quarter-final no one predicted on Wednesday.
Defending champion Federer, zeroing in on Grand Slam No 20, lines up for his 26th career meeting with the big-serving Czech in his 14th appearance at an Australian Open last eight.
The 36-year-old Swiss legend holds a 19-6 lead over the 19th seeded Berdych dating back to their first meeting in 2004.
He is 4-0 over him in Melbourne, but Federer is taking no risks against a player who has beaten him twice at Grand Slams, at Wimbledon in 2010 and two years later at the US Open.
"We have had some good ones over the years going back all the way to the Olympic Games in Athens in 2004," Federer said.
"I'm looking forward to play against him. He seems in good shape and I'm happy he's over his back issues that he also had at the end of last year."
Federer is shaping up for another potential final with world No 1 Rafael Nadal, but first he must get past Berdych and then either surprise packages Chung or Sandgren.
The Swiss star is coming off an extraordinary 2017, when he won a fifth Australian Open title and a record eighth at Wimbledon and in his four wins so far looks in the mood to carry it on into 2018.
For Berdych playing Federer is "extremely tough", but he says it's another opportunity for him on the Grand Slam stage.
"I'm definitely going to go out there, try my best, try to play good tennis, and believe in myself that I can do it," he said.
"I did it in the past and I did it in the slams, so I know how it is to beat him for the best-of-five sets. I'll go out there and swing at some balls."
While there is something of the same old in the Federer-Berdych match-up, the same cannot be said of the other intriguing quarter-final between the 58th-ranked Chung and American No 97 Sandgren.
Both have been headliners at the year's opening Grand Slam with Chung knocking out world No 4 Alexander Zverev and 12-time Grand Slam champion Novak Djokovic, while Sandgren toppled former winner Stan Wawrinka and world No 5 Dominic Thiem.
Chung, 21, pulled off his greatest win over an ailing Djokovic to become the first South Korean player to reach a Grand Slam quarter-final.
Sandgren, 26, had never won a Grand Slam match before reeling off four stunning victories to reach the last eight.
The Korean has won their only meeting in three sets in the first round in Auckland this month.
"He's really good player. He's made his first quarter-final, same like me. I'm just have to be ready for him," Chung said.
Sandgren has had an extraordinary time in Melbourne after failing to qualify for the last four Australian Opens.
"I've definitely had a real pinch-me moment. Wow, this is hopefully real. If I wake up now, I'm going to be real upset," he laughed.
"With each match I feel like I'm getting more confidence, sure of the things I'm good at."
At the end of their unique match, one of them will be
playing in the semi-finals of the Australian Open.