British number two Emma Raducanu retired from her Korea Open quarter-final against Daria Kasatkina with a foot injury.
Raducanu struggled with the issue in the previous round against Yue Yuan and continued to look uncomfortable in the opening exchanges against Russian top seed Kasatkina.
The 21-year-old needed a medical time out after the fifth game and decided she could not continue after losing the opening set 6-1.
Kasatkina will play compatriot Diana Shnaider or Ukraine's Marta Kostyuk in the semi-finals, which will take place later on Saturday after rain postponed play on Friday.