Dumped out of the Brisbane International last week, Ashleigh Barty retains a comfortable cushion of 1,607 points over Karolina Pliskova, who went on to win the Brisbane title.
No explanation was given by officials who confirmed Novak Djokovic's absence from the ATP-WTA tournament, whose women's field is headed by top-ranked Ashleigh Barty.
On Monday, air quality in Melbourne was downgraded from 'very poor' to 'hazardous', prompting health warnings from authorities.
Simona Halep moves up to third without playing thanks to Naomi Osaka losing points due to the later start this year of the Brisbane tournament.
Top-ranked Rafael Nadal and Ashleigh Barty lead the field at the 115th edition of the Australian Open from January 20-February 7.
Ashleigh Barty won four titles in 2019 including the prestigious WTA Finals and finished the year on top of the WTA rankings.
Fed Cup: France's Kristina Mladenovic and Caroline Garcia beat Australia's Ashleigh Barty and Samantha Stosur in the deciding doubles match in straight sets.
Fed Cup Final: Ashleigh Barty kept her cool in the searing heat to embarrass a stunned Caroline Garcia in a rare double bagel.
Ashleigh Barty claimed a record-setting US$4.42 million paycheque - the largest sum ever awarded in men's and women's tennis.
Ashleigh Barty, playing in her WTA Finals debut, will look to cap off a momentous season when she plays Elina Svitolina in Sunday's final.
Ashleigh Barty and Belinda Bencic both advanced to the semi-finals after contrasting victories at the WTA Finals in China.
WTA Finals: Kiki Bertens won 3-6, 6-3, 6-4 in two hours and nine minutes in a see-saw match featuring 12 breaks of serve.
Naomi Osaka, who retired during last year's edition of the WTA Finals with a hamstring injury, had been due to play World No.1 Ashleigh Barty later on Tuesday.
Ashleigh Barty has joined legends like Cathy Freeman and Ian Thorpe in lifting the prestigious prize.
China Open: Naomi Osaka fought back from a set down to defeat world number one Ashleigh Barty to clinch the title.
China Open: Naomi Osaka said that she felt she had been "counted out" after hitting poor form following her Australian Open triumph in January.
WTA Rankings: Ashleigh Barty once again retained the top spot in but will have to produce her top performance at Wuhan Open to retain her No. 1 spot.
Belgium's Elise Mertens and Belarusian Aryna Sabalenka captured their first Grand Slam title Sunday by winning the US Open women's doubles final.