HALLE, Germany, June 22 (Reuters) - World number nine Kei Nishikori's Wimbledon preparations suffered a setback on Thursday when he was forced to retire injured from his Halle Open round of 16 match against Russian Karen Khatchanov.
The third seed needed to take a medical time-out to treat a back injury before playing on for a few points and retiring with the score at 3-2 in the first set for the Russian.
Wimbledon, the only grand slam to be played on grass, starts on July 3.
Khachanov will now play the winner of the match between fellow Russians Mikhail Youzhny and Andrey Rublev. (Reporting by Karolos Grohmann; Editing by Gareth Jones)