Canada’s Bianca Andreescu, who in 2019 defeated Williams in the US Open final, was back to her winning ways against Romania’s Mihaela Buzarnescu.

She recorded a 6-2 4-6 6-3 victory, her eighth consecutive at a slam.

The 20-year-old picked up where she left off, winning her first match in 15 months —- since the New York final.

She had skipped the whole 2020 season due to injury and opted out when the tour resumed after a break due to the coronavirus pandemic.

Earlier in the day, it took American 10th seed Williams under an hour to get through Siegemund after dropping serve in the opening game.

She will next face unseeded Serbian Nina Stojanovic in the second round of the Australian Open.

“This was a good start. Definitely vintage ‘Rena,” the 39-year-old said. “It’s definitely good. I think I’m pretty good at pacing myself in a Grand Slam.

On the men’s side, US Open champion Dominic Thiem of Austria dispatched Kazakh Mikhail Kukushkin 7-6 (7-2) 6-2 6-4 in under three hours.

Last year’s semi-finalist Alexander Zverev, Stan Wawrinka and Milos Raonic also made it safely into round two.

Three-times grand slam champion and 2019 Melbourne champion Osaka took just 68 minutes to defeat Russia’s Pavlyuchenkova, a quarter-finalist at the Australian Open in three of the past four years.

But the 2016 champion Angelique Kerber was an early casualty, routed by American Bernarda Pera 6-0 6-4.

Kerber was among the players who were not permitted to leave their hotel rooms at all for two weeks after arriving in Australia.

This was because other passengers aboard their charter flights had tested positive for the new coronavirus.

All players and their entourages had to quarantine for two weeks upon their arrival in Australia, but most competitors were allowed to train for five hours a day.

was reportedly also among the players in hard lockdown.

“Last year was very crazy for the world, and to be able to do what I love and to be able to come out and compete and play at a Grand Slam, after the last 12 months, it makes me appreciate the moment even more,” Serena Williams said.

In the opening match at Margaret Court Arena, Serena’s 40-year-old sister Venus Williams defeated Kirsten Flipkens 7-5 6-2, while French Open champion Iga Swiatek ousted Dutch Arantxa Rus 6-1 6-3.

On the men’s side, big-serving Canadian Raonic made quick business of Argentina’s Federico Coria 6-3 6-3 6-2.

Also, last year’s Melbourne semi-finalist Zverev overcame an early hiccup to defeat Marcos Giron of the US 6-7 (8-10) 7-6 (7-5) 6-3 6-2.

Three-times grand slam champion Wawrinka dismissed Portugal’s Pedro Sousa 6-3 6-2 6-4 in just over 90 minutes at the newly renamed John Cain Arena, formerly Melbourne Arena.

Young Finn Emil Ruusuvuori saved 17 of 23 break-points and stunned 10th seed Gael Monfils 3-6 6-4 7-5 3-6 6-3 in three hours and 46 minutes to win in his Australian debut.