Top seed Sofia Kenin reached the last 16 of the WTA Abu Dhabi Open on Friday after opponent Kirsten Flipkens suffered an ugly-looking ankle injury when she collided with an advertising sign.
Australian Open champion Kenin dropped the first set 7-5 but was leading the second 5-4 when her Belgian rival was forced to retire.
“I obviously got a little bit upset, emotional,” said world number four Kenin after the second round tie.
“We’re good friends and that’s not something you like to see. I just hope she can have a speedy recovery and get ready for Australia. I’ll write to her later tonight, asking how she is.”
The 86th-ranked Flipkens, a former top 20 player and 2013 Wimbledon semi-finalist, was hurt as she collided with an advertising block at the back of the court as she leapt for the ball.
Her left ankle turned over and she collapsed to the ground in acute pain.
Kenin will now face 13th-seeded Yulia Putintseva for a place in the last-eight after the Kazakhstan player defeated Barbora Krejcikova of the Czech Republic in straight sets.