The young man, who has idolised Federer, handed him his first defeat in Melbourne in two years. Federer was ousted 6-7 (11-13), 7-6 (7/3), 7-5, 7-6 (7/5) at the Rod Laver Arena.
Andy Murray conceded to the press ahead of the Australian Open that he is in a lot of pain and the grand slam in Melbourne could well be his last tennis tournament.
The 37-year-old American achieved her victory over sister Venus in the final two years ago while eight weeks pregnant with her daughter Alexis Olympia.
Federer faces a tricky test against world number five Alexander Zverev in Saturday's semi-final in London. Here's how you can watch the match live on TV, online.