Meanwhile, Paula Badosa takes on Australian No. 2 Ajla Tomljanovic in her first Grand Slam as a Top 10 player.

“I really wanted this win and to have to come back from losing a bunch of games in a row is what I’m most proud of,” Keys told courtside interviewer Andrew Krasny.

There are 32 major titles represented in the bottom half, and just one on the top half. However, the task at hand will not be an easy one for the Croatian.

Based on how it all went, you’d think the 65th-ranked Estonian was the one who’d won this title 12 months ago.

Also, Feliciano Lopez rallied to win from two sets down for the fifth time in his career. Earlier, Shelby Rogers eased past Olga Danilovic with Novak Djokovic in the stands.

The 2019 Australian Open champion breezed through her first match of the 2021 season, while Aryna Sabalenka saw her 15-match winning streak conclude against the always-dangerous Estonian.

These five players had the hunger and finishing power to get the better of their seeded opponents.

The world No. 1 avenged a first-round loss to the hard-hitting Estonian at the 2018 US Open with a 6-7 (2), 6-4, 6-2 victory in the first round of the very next major.

Before play began in Melbourne, tennis legend Rod Laver lit the spires of New York City's One World Trade Center in Australian colors.