Stan Wawrinka fights through while Felix Auger-Aliassime is knocked out.
Wawrinka ensured his safe passage into the second round following a hard-fought 7-5 ,6-7 (4), 6-4, 6-4 win over Damir Dzumhur.
The highly-rated 19-year-old Canadian Auger-Aliassime has been knocked out by qualifier Ernests Gulbis 7-5, 4-6, 7-5 (4), 6-4.
Rafael Nadal is through after beating the world number 72 Hugo Dellien 6-2, 6-3, 6-0 in just over two hours on Rod Laver.
Dominic Thiem eased past Adrian Mannarino into the second round thanks to a 6-3, 7-5, 6-2 win over the unseeded Frenchman.
Fabio Fognini managed to turn around his match against Reilly Opelka and completed a stunning 3-6, 6-7(3), 6-4, 6-3, 7-6(5) victory.
Australian John Millman progressed with a 7-6(3), 6-3, 1-6, 7-5 win against Ugo Humbert as well as compatriot John Millman who fought past the "Kyrgios of Kazakhstan" Alexander Bublik 6-4, 6-3, 6-2.
Another Australian wild card, 22-year-old Marc Polmans, overcame Mikhail Kukushkin 6-4, 6-3, 4-6, 6-7 (8-10), 6-4.
The shaggy-haired 18-year-old Jannik Sinner, who won the ATP's Next Gen championship in November, finished off Australian qualifier Max Purcell 7-6(2) 6-2 6-4.
Roberto Bautista-Agut, who went unbeaten during Spain's run to the ATP Cup final, dispatched countryman Feliciano Lopez 6-2 6-2 7-5.
Canadian Milos Raonic eased past lucky loser Lorenzo Giustino 6-2 6-1 6-3
American wild card Michael Mmoh beat Spaniard Pablo Andujar 6-1, 6-1, 6-4 while it was another Spaniard - Alejandro Davidovich Fokina - who defeated Norbert Gombos 4-6, 6-4, 2-6, 6-3, 6-2.
Cristian Garin beat Stefano Travaglia 6-4, 6-3, 6-4 and Mikael Ymer registered a straight sets victory against Yasutaka Uchiyama 6-4, 6-1, 6-2.
Tommy Paul overcame Leonardo Mayer 4-6, 6-4, 6-4, 6-4 and the 27th seed Pablo Carreno Busta beat Jozef Kovalik 6-4, 6-3, 1-6, 7-6 (2).
Polish 31st seed Hubert Hurkacz came back from two sets down to beat Austrian qualifier Dennis Novak 6-7 (7-4) 1-6 6-2 6-3 6-4.
Tennys Sandgren beat Marco Trungelliti 6-1, 6-4, 7-5 and Marin Cilic blitzed Frenchman Corentin Moutet 6-3 6-2 6-4 in one hour and 46 minutes.
Fernando Verdasco defeated Evgeny Donskoy 7-5, 6-2, 6-1.
Benoit Paire - who will face Cilic in the next round - required five sets to eliminate German Cedric Stebe 6-4, 3-6, 6-3, 6-7 (2), 6-0.
Russian Karen Khachanov beat Spanish qualifier Mario Vilella Martinez 4-6, 6-4, 7-6 (4), 6-3.
On Court 22, Filip Krajinovic saw off Quentin Halys 7-6 (9-7), 7-6 (1), 3-6, 4-6, 7-5.
