No.1 seed Ashleigh Barty is yet to lose to No.8 seed Kiki Bertens in four previous encounters - but three of those, including both of this year's clashes, went to three sets. Barty had to save five match points in their first meeting, in qualifying for Brisbane 2014, before winning 2-6, 6-3, 7-5 (marking her first successful navigation of WTA qualifying), and was taken all the way on home soil again this year in the Sydney semifinals before triumphing 6-7(4), 6-4, 7-5. In between those, the Australian took her only straight-sets win over Bertens 6-3, 6-1 in the 2018 Montréal quarterfinals; in their most recent tilt, she came from a set down again to win 4-6, 6-3, 6-2 in the fourth round of Miami this March en route to the title.
No.16 seed Caroline Wozniacki is yet to drop a set to No.4 seed Naomi Osaka in two previous matches - although they have not played since Osaka became a Grand Slam champion, with the Dane's victories coming 7-5, 6-3 in the 2016 Tokyo final and 6-2, 7-6(5) in the second round of Eastbourne 2017.
Both Ashleigh Barty and Kiki Bertens are bidding to reach their fifth final of the season. So far, Barty is 4-2 in semifinals in 2019, while Bertens is 4-4. Meanwhile, Naomi Osaka is seeking to reach her third final of the year, and is 2-1 in last-four matches in 2019 (having not played her Stuttgart semifinal due to giving a walkover).
2010 and 2018 champion Caroline Wozniacki, who is going for her 56th career final and second of the year following Charleston, is the only player remaining to have contested a Beijing final, and is bidding to become the first player to successfully defend a Beijing title. Only two players have previously reached back-to-back finals here - Jelena Jankovic in 2007-08 and Svetlana Kuznetsova in 2008-09 - and none since it became a Premier Mandatory event in 2009. The Dane is on a 10-match and 20-set winning streak at the China Open, with her last defeat coming in the third round in 2017 at the hands of Petra Kvitova.
Osaka champion Naomi Osaka, who has reached her second straight semifinal in Beijing, is on an eight-match winning streak. The Japanese player's record winning streak to date is 10, compiled as she won the US Open and reached the Tokyo final in 2018. Today, she is bidding to reach consecutive title matches for the second time in her career.
Kiki Bertens is seeking to notch up a second victory over a reigning World No.1 to add to her defeat of Simona Halep in the 2018 Cincinnati final.
Caroline Wozniacki is attempting to preserve her streak of having reached at least two finals in every year since 2008, the year she made her first four finals. The former World No.1 will also bid for her first Top 10 win of the season against Naomi Osaka; her last win over a player in that echelon was against Petra Kvitova in the round-robin stages of last year's WTA Finals.
Naomi Osaka's quarterfinal win over Bianca Andreescu secured her second consecutive appearance at the WTA Finals in Shenzhen. Kiki Bertens will need to win the title this week to be sure of qualifying.
ORDER OF PLAY
DIAMOND (starts 12.30pm)
Jelena OSTAPENKO (LAT) / Dayana YASTREMSKA (UKR) vs Karolina PLISKOVA (CZE) / Kristyna PLISKOVA (CZE)
Not before 2.30pm
 Ashleigh BARTY (AUS) vs  Kiki BERTENS (NED)
After 1 ATP match, not before 7.30pm
 Naomi OSAKA (JPN) vs  Caroline WOZNIACKI (DEN)
LOTUS (starts 2pm)
[WC] Sofia KENIN (USA) / Bethanie MATTEK-SANDS (USA) vs Shuko AOYAMA (JPN) / Ena SHIBAHARA (JPN)