Play begins at 1:30 p.m.
 Timea BABOS (HUN) / Andrea HLAVACKOVA (CZE) vs Andreja KLEPAC (SLO) / Maria Jose MARTINEZ SANCHEZ (ESP)
Not Before 4:00 pm
 Karolina PLISKOVA (CZE) vs  Jelena OSTAPENKO (LAT)
Not Before 7:30 pm
 Garbiñe MUGURUZA (ESP) vs  Venus WILLIAMS (USA)
 CHAN Yung-Jan (TPE) / Martina HINGIS (SUI) vs Anna-Lena GROENEFELD (GER) / Kveta PESCHKE (CZE)
The second and final match from the White Group is a rematch of the Wimbledon final, in which Muguruza saved set points in a thrilling opening set en route to defeating Williams for her second Grand Slam title this summer, 7-5, 6-0.
The doubles competition gets underway on Thursday in knockout format, as top seeds and WTA Doubles Team of the Year Chan Yung-Jan and Martina Hingis take on Anna-Lena Groenefeld and Kveta Peschke, and No.3 seeds Timea Babos and Andrea Hlavackova face off against Andreja Klepac and María José Martínez Sánchez.
Muguruza will look to return to the semifinals at the WTA Finals for the second time, after doing so in her debut in 2015. The Spaniard was knocked out in the group stage a year ago.
On the other hand, Williams will look to return to the last four for the first time this decade, dating back to a runner-up showing to sister Serena in Doha in 2009. The American qualified for the WTA Finals this year for the first time since 2010, when she was forced to withdraw due to injury.
The objective for Muguruza and Williams is simple: win, and you're in. The winner of the Wimbledon final rematch will be the second qualifier out of the White Group behind Karolina Pliskova, who confirmed her spot on Tuesday.
"Every match is tough match here, because all the players who got here, they play at very high level. I...play one more match, and I'm just going to try to enjoy it." - Jelena Ostapenko, who cannot advance to the semifinals in her debut appearance in Singapore regardless of the result against Pliskova.
Garbiñe Muguruza, following Tuesday defeat against Pliskova: "I'm not a super friend of this round robin [format], but now it can help me turn things around. I'm going to try to do everything I can to be different than today. It's the last chance and try to take it."
RECAP FROM WEDNESDAY IN THE RED GROUP