Top seed Elena Dementieva reached the semi-finals of the Family Circle Cup on Friday when Dominika Cibulkova retired in the second set because of a left thigh strain.
The Russian, who had lost only four games in her two previous matches, was leading 6-4, 1-0 in the quarter-final when the seventh-seeded Slovakian retired.
Cibulkova ended her bid due to a left thigh injury.
Olympic champion Dementieva will next meet Denmark's Caroline Wozniacki, who beat France's Virginie Razzano 6-2, 6-0.
It will be the fourth meeting between the two players as Dementieva has a 2-1 advantage in the matchup.
In other action, sixth-seeded Marion Bartoli knocked off Melinda Czink 6-4 6-1, while Sabine Lisicki beat Elena Vesnina 6-4, 6-0.
Bartoli and Lisicki will meet in the second semi-final with Bartoli holding a 1-0 advantage over her opponent.
Bartoli has won four tour titles and made the Wimbledon final two years ago.