World No.56 Chung, the first South Korean to advance into the singles semi-finals of a Grand Slam tournament, pulled the plug after feeling pain in his left foot, reports Efe.
The 21-year-old Chung is the result of an effort to try to change this.
It pitched Federer into his seventh Australian final as he chases his sixth Melbourne title and a record 20th Grand Slam victory.
Federer, who spent just over an hour on court, will play No. 6-seeded Marin Cilic in the final on Sunday night. "At what stage, how much, we will see".
But barring his knee injury in 2016, Federer has mostly been in good health in his career and the nature of Friday's tussle means he'll be well rested for his clash with Cilic in a repeat of the Wimbledon final as he bids for a landmark 20th major.
The reverse was the case at Flushing Meadows two years later when Novak Djokovic claimed a thrilling semi-final comeback win over Federer before seeing off Nadal in the title decider.
"From what I've heard, it's blowing up in Korea pretty big", Chung's coach, Neville Godwin, said Thursday at Melbourne Park.
Chung's agent Stuart Duguid later revealed the Korean's foot was "red raw" after days of blisters which pain-killing injections had failed to numb. Because he has played so many matches in the row, I think that's why it was a build-up.
'I was there first, I think, and I was told that Marin was coming.
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Chung only lasted a bit more than two games before pulling out to a stunned silence.
You'd hope that with the finals next up the network has heard the voices of tennis fans and won't miss any more games due to excessive advertising.
"I'm playing much, much more aggressive", Cilic said. He upset No. 4-seed Alexander Zverev and six-time champion Novak Djokovic en route to becoming the first Korean tennis player, male or female, to reach the semifinals of a major.
"He is already a great player but we are talking about next-level excellence and I think he's going to achieve that", Federer said. I've played with blisters in the past a lot and it hurts a lot. I [am] going to play on the court.
With the Australian Open promoting itself as the Grand Slam of Asia-Pacific, Duguid said it's a ideal opportunity for Chung to pursue opportunities with companies back home.
Cilic overcame him on the way to winning the 2014 US Open final, but it is his only win in nine encounters and the Swiss defending champion has glided to the brink of another title without dropping a set.
Chung's ranking is set to rise into the top 30 next week, just a couple spots below another of his idols, Kei Nishikori of Japan, a former U.S. Open finalist. "I'm just really happy".
"I make first round 16, quarters and semis". I'm incredibly happy to be in the final, but not like this.