CANCHA CENTRAL -- 2:00 p.m. start
 Magdalena RYBARIKOVA (SVK) vs. Sachia VICKERY (USA)
 Kristina MLADENOVIC (FRA) vs.  Garbiñe MUGURUZA (ESP)
Not before 7:00 p.m.
 Angelique KERBER (GER) vs.  Kirsten FLIPKENS (BEL)
 Anastasia PAVLYUCHENKOVA (RUS) vs.  Victoria AZARENKA (BLR)
CANCHA 4 -- 2:00 p.m. start
Ana BOGDAN (ROU) / Elena-Gabriela RUSE (ROU) vs. Sharon FICHMAN (CAN) / Erin ROUTLIFFE (NZL)
Kristina Mladenovic has won both of her previous matches against defending Abierto GNP Seguros champion Garbiñe Muguruza, but this will be their first encounter on hardcourt.
Muguruza defeated 2012 champion Timea Babos to win the Abierto GNP Seguros last year -- which was the Spaniard's only title of 2018.
Top seed Angelique Kerber takes a 3-0 head-to-head lead into her meeting with Kirsten Flipkens. Two of Kerber's wins came at Wimbledon, in 2014 and 2017.
Victoria Azarenka leads Anastasia Pavlyuchenkova 4-1 in their head-to-head, but they have not played each other since 2015. Azarenka is making her Monterrey debut this week, while Pavlyuchenkova is 24-2 and has won four titles at this event.
Sachia Vickery and Magdalena Rybarikova will contest a rematch of their Monterrey quarterfinal from last year, which is their only previous meeting. Vickery triumphed in that match, 6-0, 6-3.