Iga Swiatek survived a tough test against former Australian Open champion Sofia Kenin to reach the second round in Melbourne on Tuesday.
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The Polish world No 1 came through 7-6 (7/2), 6-2 against the player she beat to win her first Grand Slam title, at the French Open in 2020.
In-form Swiatek, 22, twice came back from a break down in a gruelling first set lasting 68 minutes but stepped on the gas in the second set, winning the final five games to finish with a flourish.
The four-time major winner, now on a 17-match winning streak, will face either America's Danielle Collins or former winner Angelique Kerber next.
"Really happy, it's not easy to play the first match, especially the first Grand Slam of the season," said Swiatek, who owns three Roland Garros crowns and another at the US Open.
"Wasn't easy at the beginning to find my rhythm and I felt a little bit off and Sofia did everything to keep it that way.
"I'm happy that I managed to get through the second set."
There was also a first-round win for former US Open champion Sloane Stephens, who brushed aside Australian wildcard Olivia Gadecki 6-3, 6-1.