Seoul - Varvaro Lepchenko upset world number five Agnieszka Radwanska for the second time in two meetings as she ended the Pole's title defence in the WTA Korea Open quarter-finals on Friday.
Lepchenko lost an opening-set tiebreaker but she came back with a vengeance to win 6-7 (4/7), 6-2, 6-2 and set up a semi-final against fellow American Christina McHale.
The result means former Wimbledon champion Radwanska, who also lost to Lepchenko in July, is still yet to successfully defend any one of her 14 career titles.
Former Korea Open winner Maria Kirilenko, playing on a wildcard as she pursues her comeback from injury, beat Estonia's Kaia Kanepi 6-7 (3/7), 6-2, 6-3.
The Russian set up a semi-final against Czech second seed Karolina Pliskova, who beat America's Nicole Gibbs in straight sets.