For the second year running, No.2 seed Karolina Pliskova and No.8 seed Elina Svitolina are in the same group at the WTA Finals. Last year, in their most recent encounter, Svitolina won their round-robin match 6-3, 2-6, 6-3 en route to lifting the trophy - her third straight defeat of Pliskova, having lost to the Czech in their first five meetings.
Every time Svitolina has beaten Pliskova, the Ukrainian has gone on to win the title: as well as last year's clash, she also won their 2017 Rome quarterfinal 6-2, 7-6(9) and their 2018 Brisbane semifinal 7-5, 7-5. A win today would be Svitolina's first Top 5 win since defeating Petra Kvitova and Caroline Wozniacki in the WTA Finals group stages last year.
The first of Pliskova's five wins in the series came 6-4, 6-3 in the 2011 Prerov ITF 25K semifinals, and the most recent 6-2, 6-4 in the 2017 Brisbane semifinals, and in between included both of their previous matches on Chinese soil - 2-6, 6-4, 6-4 in the third round of Wuhan in 2015, and 6-3, 6-1 in the Zhuhai Elite Trophy semifinals in the same year.
No.4 seed Bianca Andreescu's clash with No.5 seed Simona Halep is one of two first-time encounters to take place at the WTA Finals this year, alongside Ashleigh Barty and Belinda Bencic's much-anticipated matchup yesterday. WTA Finals debutante Andreescu is bidding for her ninth Top 10 win in 10 such matches this year, with Naomi Osaka the only player in that echelon to have beaten the Canadian so far.
US Open champion Andreescu's match against Wimbledon champion Halep will be just the third encounter between reigning Grand Slam victors this season, following Australian Open champion Naomi Osaka's defeats of Andreescu and Roland Garros champion Ashleigh Barty in the Beijing quarterfinals and final respectively last month.
Svitolina is seeking to become the first player to successfully defend a WTA Finals title since Serena Williams's hat-trick of trophies between 2012 and 2014 across two host cities, Istanbul and Singapore.
At 19 years old, Andreescu is the youngest qualifier for this year's WTA Finals, and the first teenager to do so since a 19-year-old Caroline Wozniacki in 2009. Andreescu is also the fourth Canadian in history to compete at the WTA Finals, following Carling Bassett-Seguso in 1984 and 1985, Helen Kelesi in 1988 and 1989 and Eugenie Bouchard in 2014.
ORDER OF PLAY (starts 4pm)
 Timea BABOS (HUN) / Kristina MLADENOVIC (FRA) vs  CHAN Hao-Ching (TPE) / Latisha CHAN (TPE)
Not before 6.30pm
 Karolina PLISKOVA (CZE) vs  Elina SVITOLINA (UKR)
Not before 8pm
 Bianca ANDREESCU (CAN) vs  Simona HALEP (ROU)
 Elise MERTENS (BEL) / Aryna SABALENKA (BLR) vs  Anna-Lena GROENEFELD (GER) / Demi SCHUURS (NED)