Top seed Ons Jabeur moved through to the MUSC Health Women's Open semi-finals after easing past Nao Hibino.
Jabeur – eyeing her first WTA Tour title – made light work of Hibino 6-0 6-1 in Charleston on Friday.
Next up for the Tunisian is high-flying Danka Kovinic at the WTA 250 tournament.
For the second week in a row, Kovinic reached the semi-finals in Charleston after taking down hometown favourite and third seed Shelby Rogers 7-5 6-1.
Maria Camila Osorio Serrano, who claimed her maiden singles title at the Copa Colsanitas in Bogota last week, was leading 6-4 1-0 when Clara Tauson retired.
Meanwhile, Astra Sharma defeated 15-year-old Czech Linda Fruhvirtova 6-4 6-3.