Madison Keys of the United States was forced to retire in the second set of her Wuhan Open second round match against Germany's Angelique Kerber on Tuesday.
Keys retired at four games to one down in the second set after picking up an injury to her left knee, reports Efe.
Kerber, the reigning Wimbledon champion, had swept the world number 18 aside in the first set 6-0, during which Keys hit 22 unforced errors.
The American was finally able to get on the scoreboard early in the second set, but could not overcome her injury to get a foothold in the match and trouble her opponent.
Kerber moves on to the third round, where she will face either Saisai Zheng of China or Australia's Ashleigh Barty.