No.2 seed Elina Svitolina leads her head-to-head against Yulia Putintseva 4-2 - with Putintseva winning two ITF encounters in Tyumen in 2011 and Dubai in 2012, but Svitolina since winning the last four at Tour level: three matches in 2015 (the first round of the Australian Open, the second round of Roland Garros - a 1-6, 7-5, 9-7 epic - and the first round of Beijing) and a 6-2, 6-2 win in the second round of Moscow 2016.
Alison Riske also leads the head-to-head against Zheng Saisai 4-2, but on hard courts the pair are all square at 2-2, with San Jose champion Zheng winning the last two. After a pair of early straight-sets wins for Riske in Australian Open qualifying in 2013 and the 2014 Tianjin semifinals, the American's only wins have come on grass, with Zheng taking their first-round tilts at Tokyo 2015 and Hiroshima 2018.
Alison Riske's superb upset of No.5 seed Angelique Kerber in the first round was the third time this season that the 29-year-old has saved at least one match point before winning, following her defeats of Kiki Bertens in the 's-Hertogenbosch final (saving five match points) and Maria Sakkari in the first round of Toronto (saving three match points). The only other player to save match point en route to winning on three occasions in 2019 WTA main draws is Donna Vekic.
No.3 seed Kiki Bertens is 2-0 against Ajla Tomljanovic - but both of their matches have gone the distance, with the Dutchwoman winning 4-6, 6-1, 6-1 in the first round of Roland Garros 2017 and 7-6(2), 4-6, 6-2 in last year's Seoul final.
In a big-hitting affair, No.4 seed Aryna Sabalenka will face 2017 Roland Garros champion Jelena Ostapenko for the first time. Ostapenko is bidding for her first Top 20 win off grass since Miami 2018.
ORDER OF PLAY
CENTRE COURT (starts 2pm)
Jelena OSTAPENKO (LAT) vs  Aryna SABALENKA (BLR)
Yulia PUTINTSEVA (KAZ) vs  Elina SVITOLINA (UKR)
ZHENG Saisai (CHN) vs Alison RISKE (USA)
Not before 7pm
 Kiki BERTENS (NED) vs Ajla TOMLJANOVIC (AUS)
Monique ADAMCZAK (AUS) / HAN Xinyun (CHN) vs Lesley PATTINAMA KERKHOVE (NED) / Bibiane SCHOOFS (NED)
COURT 1 (starts 3pm)
Sofia KENIN (USA) / Asia MUHAMMAD (USA) vs Yanina WICKMAYER (BEL) / Tamara ZIDANSEK (SLO)
Not before 6.30pm
 Darija JURAK (CRO) / Alison RISKE (USA) vs Desirae KRAWCZYK (USA) / Ellen PEREZ (AUS)