Serena Williams made a storming return to the grand slam stage to set up a second-round clash with a resurgent Eugenie Bouchard.
The Canadian, who soared into the top 10 in 2014, dropped as low as 193 in the rankings last season but has worked her way back into double figures and a 6-2 6-1 victory over Peng Shuai earned her a shot at the title favourite.
Williams played her first competitive match since her tumultuous defeat by Naomi Osaka in the US Open final in September and was in devastating form, beating neighbour and fellow mother Tatjana Maria 6-0 6-2 in just 49 minutes.
Bouchard admitted she had her eye on a clash with Williams as soon as the draw was made.
She said: "I'm super excited. This is why we play the big tournaments, to play the best players.
"She's the greatest ever. I admire obviously the longevity of her career, her dominance over such a long amount of time, how she's come back so many times from injury, pregnancy, etc.
"I don't want to talk about it too much and put her on too much of a pedestal because I have to play her in two days, but I love her."
Bouchard struggled to cope with the weight of expectation after her rapid rise, but, even during her difficult times, she has shown the ability to rise to the big occasion.
Still only 24, Bouchard said: "I'm enjoying the training and enjoying the matches. That's the most important thing, because I have definitely had moments where I didn't enjoy it so much. I knew deep down that I still believed in myself and my game and I'm still relatively young."
Williams extended her winning streak in Melbourne to eight matches, having won the title on her last appearance in 2017 while in the early weeks of pregnancy.
Dressed in a striking green playsuit that she dubbed the "Serenatard", the 37-year-old, who continues to chase a record-equalling 24th slam singles titles, dropped only five points in the first set.
The victory ended a five-match losing streak for the top seed, who was troubled by a back problem at the end of last season.
The Romanian, the runner-up 12 months ago, said: "I don't want to remember about that match (in New York) because it was a tough one. I knew she's a very tough opponent. It was good for me tonight and I'm really happy I can play the second round."
Venus Williams looked to be heading out of the tournament at a set and 5-3 down to 25th seed Mihaela Buzarnescu, but recovered to win 6-7 (3) 7-6 (3) 6-2.
The 38-year-old said: "There were moments where it looked like maybe she had the match. That's what's great about tennis – the clock doesn't run out."
There was no happy return to the tournament she has won twice for Victoria Azarenka, who fell 6-7 (5) 6-4 6-2 to Germany's Laura Siegemund.
Azarenka was absent from Melbourne the last two years because of the birth of son Leo and the subsequent custody battle that restricted her travel, and is still searching for a return to form.
She broke down in her post-match press conference, saying: "I've been through a lot of things in my life and sometimes I wonder why I go through them, but I think they're going to make me stronger."
Fourth seed Osaka was a 6-4 6-2 winner over Magda Linette and there were victories for Elina Svitolina, Karolina Pliskova, Madison Keys and Garbine Muguruza, but 10th seed Daria Kasatkina lost 12 straight games in a 6-3 6-0 loss to Timea Bacsinszky.