Garbiñe Muguruza is aiming to become the fourth No.1 seed to make the final in Monterrey, following Jelena Jankovic in 2011 and Angelique Kerber in 2013 and 2017. However, the top seed has never won this tournament - in each of those previous title rounds, she was defeated by Anastasia Pavlyuchenkova (absent this year).
Timea Babos and Sachia Vickery's semifinal will be a rematch of their first-round qualifying match here three years ago. The Hungarian won that 6-3, 6-1, going on to qualify and reach the second round before falling to Sara Errani. Overall, Babos leads the head-to-head 2-0, having also triumphed in New Haven qualifying in 2012.
The second semifinal will be the first meeting between Garbiñe Muguruza and Ana Bogdan.
Ana Bogdan and Sachia Vickery are both aiming for their maiden WTA final today. The Romanian has previously reached semifinals in Florianopolis 2016 and Bucharest 2017, while the American is playing the second semifinal of her career in Auckland in January. The last WTA final between two maiden finalists was almost exactly one year ago in Biel/Bienne, in which Marketa Vondrousova defeated Anett Kontaveit.
Giuliana Olmos has become the first Mexican to reach a WTA final in the Open Era, partnering Desirae Krawczyk to defeat Valeria Savinykh and Yana Sizikova in the first doubles semifinal last night.
ORDER OF PLAY (starts 2pm)
ESTADIO GNP SEGUROS
 Timea Babos (HUN) vs  Sachia VICKERY (USA)
 Garbiñe MUGURUZA (ESP) vs  Ana BOGDAN (ROU)
Mariana DUQUE-MARIÑO (COL) / Evgeniya RODINA (RUS) vs Naomi BROADY (GBR) / Sara SORRIBES TORMO (ESP)