No.1 seed Ashleigh Barty plays her first match in Australia as World No.1 against qualifier Jennifer Brady. Barty is yet to lose a set to the American in two previous meetings, having won 6-3, 6-2 in the third round of Indian Wells and 6-3, 6-1 in the second round of Birmingham, both last year. Brady stretched two Top 10 players to three sets in 2019 - Petra Kvitova in Dubai and Simona Halep in Toronto - but is yet to defeat a player ranked in that echelon.
No.2 seed and defending champion Karolina Pliskova reprises her quarterfinal here last year against wildcard Ajla Tomljanovic, an up-and-down affair which Pliskova took 6-1, 1-6, 6-1 en route to her second Brisbane title. That was one of three wins the Czech would rack up over Tomljanovic in 2019; overall, she leads the head-to-head 4-1, with Tomljanovic's only win coming 6-3, 6-3 back in 2011 in the quarterfinals of the Clearwater ITF W25 event.
No.3 seed Naomi Osaka and Sofia Kenin first met exactly five years ago, when Osaka was a 17-year-old ranked World No.412 and Kenin was an unranked 16-year-old, in the second round of the Vero Beach ITF W25 qualifying. Kenin took that match 6-4, 7-5, but Osaka got a belated revenge in the first round of Roland Garros 2018, winning 6-2, 7-5. Last year, they met for the first time off clay in the Cincinnati quarterfinals, with Kenin progressing after Osaka retired trailing 6-4, 1-6, 2-0.
Qualifier Liudmila Samsonova has been quietly hitting milestone after milestone over the past six months. The Russian made her Grand Slam main draw debut at Roland Garros last year, reached her maiden WTA semifinal as a lucky loser in Palermo, and finished the year by reaching the Poitiers ITF W80 final and Limoges 125K quarterfinals. The 21-year-old has opened her 2020 campaign by scoring her first two Top 50 wins this week - over Kristina Mladenovic in qualifying and Sloane Stephens in the first round - and now faces the first Top 10 player of her career in No.5 seed Petra Kvitova.
No.6 seed Kiki Bertens leads Anett Kontaveit 2-1 overall. Kontaveit took their first meeting 6-3, 6-4 in the first round of New Haven 2016, but Bertens has squeezed out three-set victories in their two most recent encounters, 6-4, 3-6, 6-1 in the 2017 Gstaad final and 6-3, 2-6, 6-3 in the third round of Cincinnati 2018 - going on to take the title both times.
ORDER OF PLAY
PAT RAFTER ARENA (starts 11am)
 Ashleigh BARTY (AUS) vs [Q] Jennifer BRADY (USA)
[WC] Ajla TOMLJANOVIC (AUS) vs  Karolina PLISKOVA (CZE)
[Q] Liudmila SAMSONOVA (RUS) vs  Petra KVITOVA (CZE)
Not before 7pm
Sofia KENIN (USA) vs  Naomi OSAKA (JPN)
 Kiki BERTENS (NED) vs Anett KONTAVEIT (EST)
Darija JURAK (CRO) / Alicja ROSOLSKA (POL) vs Lyudmyla KICHENOK (UKR) / YANG Zhaoxuan (CHN)