Radwanska beat Elena Vesnina 6-3, 6-3 as she was good on 70 percent of her first serves, fired eight aces and won both of Vesnina's break-point chances. She advanced after finishing off both her break opportunities in the second set.
Third-seeded Yanina Wickmayer and eighth-seeded Mona Barthel also won quarterfinal matches in straight sets. Wickmayer stopped Kirsten Flipkens 6-3, 6-4 without dropping serve and Barthel defeated Johanna Larsson 6-2, 6-1 in just 44 minutes.
Jamie Hampton claimed the other spot in the semifinals by beating Kiki Bertens 6-1, 6-7 (5-7), 6-2.
Hampton draws Radwanska in one of Friday's semifinals. Radwanska has won all three of their previous matches. Wickmayer has a 2-1 career record over Barthel.
Notable deaths of 2014 [PHOTOS]
Julius Randle breaks leg during NBA debut