Brisbane International surprise package Samantha Crawford cruised to a 6-3 6-0 over Andrea Petkovic to maintain her remarkable run on Thursday.
The young American had won just two main-draw matches on the WTA Tour prior to this tournament, but has now seen off Priscilla Hon, Belinda Bencic and Petkovic without dropping a set.
After breaking twice to clinch the opener, Crawford - who will make her Australian Open debut as a wildcard later this month - romped to victory in the second.
"It happened fast. I was trying to not think about it too much, not psych myself out," said Crawford.
"I was just trying to take my time when I was serving and focusing on that, and then stayed calm."
Crawford's opponent in the last four will be former world number one Victoria Azaraenka, who was in similarly dominant form to see off eighth seed and US Open finalist Roberta Vinci 6-1 6-2.
Injuries to the top three seeds have left Angelique Kerber as the leading name left in the competition and the German secured her semi-final spot with a 6-4 6-4 win against Anastasia Pavlyuchenkova.
Kerber was on the front foot from the off in both sets, winning the opening game on her opponent's serve in each.
In the day's remaining quarter-final, sixth seed Carla Suarez Navarro came from behind to beat Varvara Lepchenko 4-6 6-4 7-5.
The Spaniard will now meet Kerber in the next round.