World number nine Kei Nishikori will miss the remainder of the tennis season after injuring his wrist.
The Japanese is unable to take part in the Cincinnati Masters or the US Open Grand Slam, which begins on August 28.
"Kei hit a serve during practice and heard a 'pop' in his wrist," BBC Sport quotes Nishikori's manager as saying.
"At this stage, we have elected not to do surgery and Kei is in a cast. After the swelling comes down in the next weeks, we will evaluate next steps."
Nishikori joins Novak Djokovic and Stanislas Wawrinka in missing the US Open.