Aryna Sabalenka makes her main draw debut in Beijing today as the freshly-crowned Wuhan champion and brand new World No.16. On her first appearance in the tournament last year, the Belarusian - who had yet to crack the Top 100 at that point - lost in the first round of qualifying 1-6, 6-1, 6-4 to Christina McHale; now, a first meeting with 2015 runner-up Garbiñe Muguruza awaits.
No.3 seed Angelique Kerber leads her rivalry with Carla Suárez Navarro 6-3, including 4-1 on outdoor hard courts. So far, since the Spaniard's victory in their first ever meeting (4-6, 6-3, 7-6(3) in the fourth round of the 2013 US Open), the pattern has been two straight Kerber wins followed by one for Suárez Navarro - with the Wimbledon champion having won the last two.
Another blockbuster second-round tie pairs Wuhan semifinalist Wang Qiang, who has won 14 of her past 17 matches, against former Roland Garros champion Jelena Ostapenko. Their head-to-head is all square at 1-1, with the Latvian taking a second-round tilt in the second round of the 2015 ITF $50,000 event in Quanzhou 0-6, 6-3, 6-1 and Wang gaining her revenge in the first round of Dubai last year 7-6(1), 6-2. Wang has only won one match in four prior main draw appearances in Beijing - over Varvara Lepchenko in 2015.
All of No.11 seed Kiki Bertens' encounters with Kirsten Flipkens have gone to a deciding set, but she has not beaten the Belgian since their first meeting, in the first round of the ITF $100,000 event in Torhout in 2010. Since then, Flipkens has won four straight, including twice this year in the quarterfinals of Nurnberg and second round of 's-Hertogenbosch. In the first round, Bertens overcame a 0-4 head-to-head deficit to defeat Sorana Cirstea, and the Cincinnati and Seoul champion has now won 22 of her past 26 matches.
Having notched up her first win in Asia since 2015 over Anastasia Pavlyuchenkova in the first round, No.9 seed Sloane Stephens will now seek to put together consecutive victories on the continent for just the third time in her career against wildcard Zheng Saisai, following a third-round showing in Beijing (defeating Aleksandra Wozniak and Eugenie Bouchard) in 2013 and a Seoul quarterfinal run in 2015 (beating Han Na-Lae and Kimiko Date-Krumm).
Defending champion Caroline Garcia will seek to maintain her unbeaten record against Polona Hercog, whom she defeated twice previously in 2015 - 6-4, 6-1 in the first round of Acapulco and 6-4, 6-7(5), 6-4 in the second round of Indian Wells.
Aleksandra Krunic was a 7-5, 0-6, 6-0 victor in her only previous hard-court encounter with Katerina Siniakova, in 2014 US Open qualifying en route to what would be the Serb's breakthrough fourth-round showing. However, Siniakova has won both their other meetings in straight sets - in the ITF $100,000 event in Prague on clay in 2014, and in Birmingham qualifying on grass in 2016.
ORDER OF PLAY (all courts start 12.30pm)
NATIONAL TENNIS STADIUM
Sloane STEPHENS (USA)  vs [WC] ZHENG Saisai (CHN)
After 2 ATP matches, not before 7.30pm
Garbiñe MUGURUZA (ESP)  vs Aryna SABALENKA (BLR)
After 1 ATP match, not before 2.30pm
Angelique KERBER (GER)  vs Carla SUÁREZ NAVARRO (ESP)
[WC] WANG Qiang (CHN) vs Jelena OSTAPENKO (LAT) 
Laura SIEGEMUND (GER) vs Anett KONTAVEIT (EST)
Kirsten FLIPKENS (BEL) vs Kiki BERTENS (NED) 
Not before 4pm
Danielle COLLINS (USA) vs Naomi OSAKA (JPN) 
[Q] Polona HERCOG (SLO) vs Caroline GARCIA (FRA) 
Dominika CIBULKOVA (SVK) vs Daria GAVRILOVA (AUS)
Aleksandra KRUNIC (SRB) vs [Q] Katerina SINIAKOVA (CZE)
Alicja ROSOLSKA (POL) / Abigail SPEARS (USA) vs Mihaela BUZARNESCU (ROU) / Monica NICULESCU (ROU)
Timea BABOS (HUN) / Kristina MLADENOVIC (FRA)  vs Alizé CORNET (FRA) / Petra MARTIC (CRO)
HSIEH Su-Wei (TPE) / Bethanie MATTEK-SANDS (USA) vs Anastasia PAVLYUCHENKOVA (RUS) / Anastasija SEVASTOVA (LAT)
Lyudmyla KICHENOK (UKR) / Katarina SREBOTNIK (SLO) vs Lucie HRADECKA (CZE) / Ekaterina MAKAROVA (RUS)