Cincinnati - Japan's Kei Nishikori has become the latest top 10 player to pull out of this week's Cincinnati Masters after the world No 9 withdrew from the US Open warm-up event due to pain from a long-standing right wrist injury.
The 27-year-old, who had been seeded fifth and given a first-round bye, had flown to the host city before making the call to withdraw.
"Unfortunately I will not be able to play in Cincy," Nishikori wrote in English on his official app.
"Today (Sunday) during practice I felt a sharp pain in my right wrist and we are now visiting with the medical specialists to discuss the diagnosis. We will provide more details after we have more information."
Nishikori joins world No 1 Andy Murray, last year's champion Marin Cilic, US Open winner Stanislas Wawrinka and 12-times major champ Novak Djokovic on the list of players skipping the event through injury.
Both Wawrinka (knee) and Djokovic (elbow) have opted to end their seasons early to recover from their ailments, while Murray (hip) faces the prospect of losing his top ranking should either Rafael Nadal or Roger Federer win the Cincinnati event.
The US Open is the final grand slam of the year and runs from August 28-September 10 in New York.