Eighth-seeded Sloane Stephens is through to the Hobart International semi-finals with a 6-3 4-6 7-5 win over fellow American and qualifier Lauren Davis.
Stephens will play Elena Vesnina of Russia in one of Friday's semi-finals. Vesnina played better in windy conditions Thursday to beat wild-card entry Jarmila Gajdosova of Australia 6-3 6-2.
"I had to be smart and in the wind you have to use it like a weapon," Vesnina said.
Ninth-seeded Mona Barthel of Germany beat Tsvetana Pironkova of Bulgaria 6-3 6-3 and will face Belgian Kirsten Flipkens, who overcame Monica Niculescu 2-6 6-4 6-0 in Thursday night's quarter-final.
The 22-year-old Barthel said she's "improved a lot" as she begins her second season on the WTA Tour.
"I feel like I learned so much last year, playing all these tournaments and playing against the top players," Barthel said.
"My serve has got better and I feel like my groundstrokes are better ... but maybe a little more confidence this year."