The two-time major champion Svetlana Kuznetsova and top-20 tennis players Kaia Kanepi and Flavia Pennetta have pulled out of the US Open starting next week.
The US Tennis Association has not given reasons for the three withdrawals.
Kuznetsova won the 2004 title at Flushing Meadows, and added the 2009 French Open championship.
She's been ranked as high as number two in the world but is currently 48th this week.
The 15th-ranked Kanepi withdrew from Wimbledon and the London Olympics because of a heel injury.
The US Open draw will be made on Friday with play to begin next week.