Victoria Azarenka beat Sofia Kenin 6-4, 7-6 (7/3) Monday to become the only former Australian Open champion left in the women's draw.
Azarenka, the 24th seed from Belarus, won her titles at Melbourne Park in 2012 and 2013, while American Kenin prevailed to lift the champion's Daphne Akhurst Cup in 2020.
With 2022 champion Ash Barty and Serena Williams both retired, and 2019 and 2021 winner Naomi Osaka missing because of her pregnancy, it meant Kenin and Azarenka were the only two previous winners in the women's singles.
But Kenin has faced a torrid time since her only Slam triumph with form deserting her as she endured a spate of injuries.
Her ranking has slid to 203 in the world and she was bidding for a first win over a top-25 opponent since beating then number 11 Petra Kvitova at Roland Garros in 2020.
Nevertheless, the veteran world number 24 Azarenka admitted she had been on edge before the encounter on Margaret Court Arena.
"It's high pressure and you wouldn't think I'd be nervous, but it means so much to me," said the 33-year-old.
"I try to work through those emotions but they happen."
Azarenka will face either Leolia Jeanjean of France or Nadia Podoroska of Argentina in the second round.