Top seed Jessica Pegula booked her spot in the WTA 500 Charleston Open semifinals following a hard-fought win over fellow American Danielle Collins on Friday.
The world No. 4 had to fight from a set down to oust the defending champion and tournament seventh seed 1-6, 6-3, 6-0 and will next face Russian Ekaterina Alexandrova for a place in the final.
Alexandrova, seeded ninth, saw off third seed Qinwen Zheng of China 6-1, 6-4.