Pumped-up defending champion Novak Djokovic survived a serious scare on Wednesday from dangerous Frances Tiafoe, who pushed him to four gruelling sets before the World No.1 prevailed.
The Serbian top seed looked in control after taking the first set, but the lightning-quick American, who reached the quarterfinals two years ago, refused to go quietly.
He bounced back to take a close second set before Djokovic dug deep to emerge a 6-3, 6-7 (3/7), 7-6 (7/2), 6-3 winner and continue his march towards a ninth Australian Open title.
Third seed Dominic Thiem eased past Germany's Dominik Koepfer 6-4, 6-0, 6-2, while local badboy Nick Kyrgios, Alexander Zverev and Gregor Dimitrov also progressed.
The big shock of the day came as 2014 champion Stan Wawrinka was knocked out by Marton Fucsovics 7-5, 6-1, 4-6, 2-6, 7-6.
Serena Williams continued her quest for a record-equalling 24th Grand Slam by strolling into the third round with a 6-3, 6-0 win over 99th-ranked Serbian Nina Stojanovic.
She was joined in the next round by French Open champions Iga Swiatek, Naomi Osaka and Garbine Muguruza.
But there were some upsets as former US Open champion Bianca Andreescu’s emotional comeback from 15 months out ended at the hands of Taiwanese veteran Su-Wei Hsieh.
Two-time Wimbledon champion Petra Kvitova’s tournament is also over after her rusty display in a 6-4, 1-6, 6-1 defeat by Romanian Sorana Cirstea.