A foot injury forced former US Open champion Emma Raducanu to retire from her Korea Open quarterfinal 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 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 easy to get injured, especially deep into these tournaments," Kasatkina said. "I wish her a speedy recovery."
Raducanu had been bidding to reach her first semifinal above WTA 250 level since winning the 2021 US Open.
The winner of the clash between fourth seed Diana Shnaider and fifth seed Marta Kostyuk will meet Kasatkina in the semi-finals later on Saturday, after rain washed out Friday's play in Seoul.
Earlier in the day, Brazilian third seed Beatriz Haddad Maia brushed aside lucky loser Polina Kudermetova 6-2 6-1 to set up a last-four clash with Veronika Kudermetova, who beat Viktoriya Tomova 7-5 6-3.