Six-time Australian Open champion Serena Williams progressed to the second round with a straight-set win over Swiss teenager Belinda Bencic.
The American, 35, beat her 19-year-old opponent 6-4 6-3 in 79 minutes in scorching conditions in Melbourne.
The world number two, attempting to win a record 23rd Grand Slam singles title, said she “has nothing to lose”.
“Every match I’m playing for fun. I get to travel the world and do what I do best – play tennis,” she added.
Williams lost the Australian Open final last year to Angelique Kerber but won Wimbledon to equal Steffi Graf’s Open era record of 22 Grand Slam singles titles.
She has barely played since the US Open last September because of injury, and lost in the second round of this month’s Auckland Classic.
But she eased doubts about her form and fitness with a typically powerful performance in temperatures of about 35C.
Safarova saves nine match points
Williams will face Lucie Safarova in the second round after the 29-year-old Czech saved nine match points before beating Belgium’s Yanina Wickmayer 3-6 7-6 (9-7) 6-1.
Safarova saved five match points on her own serve in the second set and another four in the tie-break.
“It’s not fun,” said a stunned Wickmayer. “I think she served very well on certain points and other points I didn’t go for enough.
“But it’s normal when you have match point and you want to play it a little bit safe. Then after, you realise it’s not the best option.”
Best of the rest
Fifth seed Karolina Pliskova, who beat Williams in last year’s US Open semi-finals, went through thanks to a 6-2 6-0 victory over Spain’s Sara Sorribes Tormo.
“Even when you’re not playing your best, somehow you have to win,” said the 24-year-old.
“I know I can be dangerous deep in the tournament, quarters and semis, and when there are big players I can beat them.”
Former world number one Caroline Wozniacki did not hang around as she beat Australian Arina Rodionova 6-1 6-2 in just over an hour.
The 17th-seeded Dane faces Croatia’s Donna Vekic in the second round.