Ashleigh Barty stayed on top of the Women's Tennis Association rankings despite losing in the semi-finals of the Australian Open.
Naomi Osaka suffered a surprise 6-0, 6-3 defeat to world number 78 Sara Sorribes Tormo in the Fed Cup.
Karolina Pliskova's defeat to Anastasia Pavlyuchenkova means that two of the top three seeds are now out of the women's draw at the Australian Open.
Defending champion Naomi Osaka crashed out of the Australian Open after losing 3-6, 4-6 to 15-year-old Coco Gauff in women's singles third round at the Rod Laver Arena on Friday.
Naomi Osaka overcame a mid-match fit of pique to set up a potential third-round clash with 15-year-old prodigy Coco Gauff on Wednesday.
Naomi Osaka was an early winner as she dismissed Marie Bouzkova of the Czech Republic 6-2, 6-4 in 80 minutes.
Naomi Osaka posted a picture with her 2018 US Open final counter-part Serena Williams on Twitter but what stood out was her caption.
Karolina Pliskova's third Brisbane International title in four years and her 16th on the WTA tour, stamps her as one of the favourites for the Australian Open.
Karolina Pliskova triumphed 6-7 (10/12), 7-6 (7/3), 6-2 in a two hour, 48 minute marathon and will play eighth seed American Madison Keys in the decider.
Daniil Medvedev retweeted a journalist's screenshot of a conversation with Naomi Osaka, where she said she found the Russian "interesting".
Naomi Osaka came from a break down in the third set to overcome Greece's Maria Sakkari in the first round of the WTA Brisbane International.
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.
Naomi Osaka bumped into Beyonce and her husband Jay-Z while still "depressed" after losing in the fourth round at the US Open last year.
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.
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.
Naomi Osaka maintained her unbeaten record over Petra Kvitova having won their only previous clash in a three-set classic in Melbourne.