It's been a breakthrough tournament for Chung, whose 58th ranking is expected to tumble after toppling six-time champion Novak Djokovic and world No.4 Alexander Zverev on the way to becoming the first South Korean to reach the last four at a Grand Slam.
"Chung Hyeon wrote a new chapter in South Korean sports history and brought pride and happiness to all South Koreans".
The 21-year-old wobbled when serving out the match, squandering a 40-0 lead and seeing a total of five match points disappear into a cloudless sky as world number 97 Sandgren battled gamely. "Tomas played great. I stole that one a little bit".
"I'm happy with being resilient", Sandgren said about the match, refusing to take questions.
Chung senior is himself a former tennis player and coached a high-school tennis team in Suwon for 19 years. We also met up later for drinks, I met his fiancee. "I never playing in second week in Grand Slam, so I'm really surprised".
Meanwhile, Federer plans to be aggressive ahead of his first-ever showdown against Chung.
It'll be youth versus wisdom on Friday night at the Australian Open.
It put Federer into his seventh Australian final as he chases his sixth Melbourne title and 20th Grand Slam victory. But he's not thinking that far.
"I hardly know Chung".
"When he arrived, I didn't want to bother him". "I couldn't tell what was going on with my opponent. I don't know how I'm going to do that exactly yet".
The most striking aspect of his game is his quick movement back and forth and willingness to attack at the net.
Federer was utterly dominant until that point.
"I'm excited about that. I can't finish the match, so I can't play anymore", he said. "To close it out, that was mighty impressive".
"To bounce back from a Novak match and just somehow get it done (in the quarterfinal) that's tough". That shows that he's had good composure, a great mindset. Then, you know, I think he just get more confident after he saved the first set. Federer got his chance later in the set and grabbed it to go 3-5 up after which he served out the set.
Meanwhile, Marin Cilic of Croatia advanced to his first Aussie Open final by defeating Kyle Edmund of the U.K.in their semifinal on Thursday.
And Federer has welcomed the presence of some fresh faces in the latter stages of a grand slam.