A foot injury forced former US Open champion Emma Raducanu to retire from her Korea Open quarter-final clash with top seed Daria Kasatkina after losing the first set 6-1 on Saturday.
Britain's Raducanu struggled to serve with her injured left foot, her landing leg, as she played on after a medical timeout, committing a double fault and not chasing returns across the court.
The foot injury also surfaced during 21-year-old Raducanu's round of 16 clash with Yuan Yue, where she was able to continue after a medical timeout and win 6-4 6-3.
"I feel sorry for Emma ... it's a pity to get injured, especially in the deeper stages of the tournament," Kasatkina said after the match. "I wish her a speedy recovery."
Kasatkina will play fellow Russian Diana Shnaider in the semi-finals later on Saturday, after rain washed out Friday's play in Seoul.
Fourth seed Shnaider beat Australian Open quarter-finalist and Ukrainian fifth seed Marta Kostyuk 7-6(7) 6-3 in the quarter-finals.
Brazilian third seed Beatriz Haddad Maia faces former French Open quarter-finalist Veronika Kudermetova in the other semi-final, after brushing aside Veronika's sister Polina Kudermetova 6-2 6-1 in the last eight.
Russia's Veronika beat Viktoriya Tomova 7-5 6-3 to reach her first semi-final of the year.
