CANCHA CENTRAL (starts 4pm)
 [WC] Daria GAVRILOVA (AUS) vs  Lesia TSURENKO (UKR)
Not before 8pm
Stefanie VOEGELE (SUI) vs [Q] Rebecca PETERSON (SWE)
GRAND STAND CALIENTE (starts 5pm)
Kaitlyn CHRISTIAN (USA) / Sabrina SANTAMARIA (USA) vs Monica PUIG (PUR) / Sloane STEPHENS (USA)
Not before 6.30pm
 Lara ARRUABARRENA (ESP) / Arantxa PARRA SANTONJA (ESP) vs Tatjana MARIA (GER) / Heather WATSON (GBR)
No.7 seed Lesia Tsurenko is aiming to become the third player to successfully defend a title in 2018 following Elise Mertens in Hobart and Elina Svitolina in Dubai. The Ukrainian owns a 4-0 head-to-head lead over Daria Gavrilova, having first beaten her 7-5, 6-4 in Moscow qualifying in 2011, and most recently 6-2, 6-3 in the first round of Fed Cup World Group II play last year. Only once has the Australian won a set - in a 7-6(2), 3-6, 6-3 loss in the second round of Istanbul in 2015, a tournament Tsurenko would eventually win for her maiden title.
Lesia Tsurenko and Daria Gavrilova are both playing their second semifinal of 2018; Tsurenko lost in the final four of Hobart to Mihaela Buzarnescu, while Gavrilova was defeated at this stage of Sydney by Ashleigh Barty. Overall, the Australian No.2 has a 4-3 career record in semifinals, while the Ukrainian No.2 is just 3-7 in this round.
Stefanie Voegele and Rebecca Peterson will face each other for the first time in the top-half semifinal. This week marks the Swede's debut in the last four of a WTA tournament; by contrast, it is Voegele's ninth career semifinal. The Swiss player has lost on each of the previous eight occasions: Portoroz 2009 (to Sara Errani), Memphis 2013 (to Marina Erakovic), Charleston 2013 (to Jelena Jankovic), Linz 2013 (to Ana Ivanovic), Luxembourg 2013 (to Annika Beck, via retirement), Baku 2014 (to Bojana Jovanovski Petrovic), Luxembourg 2015 (to Mona Barthel) and Istanbul 2016 (to Cagla Buyukakcay). Voegele has garnered a set in just two of those matches - to Jankovic and Jovanovski Petrovic.
Rebecca Peterson is bidding to become the first qualifier to reach the Acapulco final since Iveta Benesova beat Marta Marrero 6-1, 4-6, 6-3 in the 2004 semifinals. Benesova would go on to win her maiden title 7-6(5), 6-4 over Flavia Pennetta in the final that year. Overall, Peterson is the third qualifier to reach the last four here following Benesova and Sara Errani, who lost to Pennetta in 2007; in addition, Sesil Karatantcheva reached the semifinals as a lucky loser in 2015, losing to Timea Bacsinszky.
Both Lesia Tsurenko and Rebecca Peterson have reached the last four without dropping a set. Tsurenko has not lost more than five games in any of her matches, while Peterson has only been stretched to a 7-5 set once - in the first round of qualifying by Elitsa Kostova.