Ivo Karlovic became the oldest man into the third round since Ken Rosewall (aged 44 in 1978) as the Croatian, who turns 39 in February, beat Yuichi Sugita 7-6 (7-3), 6-7 (3-7), 7-5, 4-6, 12-10, winning with 53 aces in the event's longest match at this edition, four hours 33 minutes.
Women's second seed Caroline Wozniacki rallied from the brink of defeat, coming from 1-5 down in the final set to overhaul Croatian Jana Fett 3-6, 6-2, 7-5 for a survival win
The former world No. 1 credited her big-match experience with pulling her through against a 119th-ranked opponent who could not handle the pressure in the end.
"I feel relieved, that was crazy," Wozniacki said. "I don't know how I got back into the match, the crowd helped to pull me through this one."
Wozniacki saved two match points to hold for 2-5 in the third as she fought her way back.
"I'm very proud of the way I came back, I just tried to mentally stay focused," she said. "It was very hard, and she was playing well. All of a sudden seeing myself down, almost out of the tournament, I started playing better and started playing the tennis that I wanted to play."
Fourth seed Elina Svitolina also engineered a comeback, beating the Czech Republic's Katerina Siniakova 4-6, 6-2, 6-1.
The Ukrainian winner of this month's Brisbane event, who lost just one set en route to her 10th career title, remains unbeaten so far in 2018.
"It was very tough for me today," Svitolina said. "I was not feeling great and was not focused on the right things."
She next takes on 15-year-old prodigy Marta Kostyuk, reigning junior Australian Open champion and youngest player to reach the third round at Melbourne since 1997, who beat local wild-card Olivia Rogowska 6-3, 7-5.
Belinda Bencic failed to follow up on her ouster of 2017 finalist Venus Williams, with the Swiss falling 6-1, 6-3 in an upset to Thai qualifier Lusika Kumkhum.
Bencic, ranked 78th after coming back from five months of wrist injury problems last season, said her game fell apart against an opponent standing 124th.
French Open winner Jelena Ostapenko, seeded seventh, defeated China's Duan Ying Ying 6-3, 3-6, 6-4.
(c)2018 Deutsche Presse-Agentur GmbH (Hamburg, Germany)
Visit Deutsche Presse-Agentur GmbH (Hamburg, Germany) at www.dpa.de/English.82.0.html
Distributed by Tribune Content Agency, LLC.