Victoria Azarenka was edged in the WTA Mexican Open quarter-finals, while Donna Vekic continued to shine in Acapulco.
Playing in her first quarter-final of the year, Azarenka went down to American fifth seed Sofia Kenin 6-4 4-6 7-5 on Thursday.
Kenin served 13 double faults, but she managed to break eight times to battle through in two hours, 32 minutes.
Enjoying a blistering start to the year, including winning her maiden WTA Tour title in Hobart, Kenin, 20, will next face Bianca Andreescu.
Canadian teenager Andreescu upstaged seventh seed Zheng Saisai 7-6 (7-3) 6-1.
The other semi-final will be between Croatian third seed Vekic and Wang Yafan.
Vekic is yet to drop a set at the WTA International event and her form continued with a 6-3 7-5 win over Johanna Konta.
Wang has also cruised through and had no problems getting past qualifier Beatriz Haddad Maia 6-3 6-4.
At the Oracle Challenger Series at Indian Wells, Kristyna Pliskova, Zarina Diyas and Wang Qiang moved into the quarter-finals.