Play starts at 4pm
GRAND STAND CALIENTE
Sloane Stephens (USA)  v Stefanie Voegele (SUI)
Veronica Cepede Royg (PAR) v Daria Gavrilova (AUS) 
Lesia Tsurenko (UKR)  v Kristina Mladenovic (FRA) 
Shuai Zhang (CHN)  v Rebecca Peterson (SWE)
Tatjana Maria (GER) / Heather Watson (GBR) v Desirae Krawczyk (USA) / Giuliana Olmos (MEX)
Anna Smith (GBR) / Renata Voracova (CZE)  v Kaitlyn Christian (USA) / Sabrina Santamaria (USA)
Dalila Jakupovic (SLO) / Arantxa Rus (NED) v Monica Puig (PUR) / Sloane Stephens (USA)
Ana Sofia Sánchez (MEX) / Renata Zarazua (MEX) v Lara Arruabarrena (ESP) / Arantxa Parra Santonja (ESP) 
Sloane Stephens has lost three of her four previous matches against Stefanie Vogele, her Tokyo victory five years ago her sole success amid defeats in Linz and Luxembourg in the same year and another loss at the 2008 US Open.
Shuai Zhang hopes to maintain her winning record against Rebecca Peterson, having beaten the Swede in their previous meeting, in Honolulu last year.
Veronica Cepede Royg faces Daria Gavrilova for the first time.
Lesia Tsurenko takes on Kristina Mladenovic in a rematch of last year's Acapulco final. The Ukrainian's victory last March was her fifth in sixth matches against the Frenchwoman, whose only victory over Tsurenko came in Dubai in 2016.