The US Open is at the end of August, but the tennis star has not said if he'll play after pulling out of this month’s Toronto Masters and Western & Southern Open.
Serena said her leg injury from Wimbledon is still bothering her while Venus did not disclose a reason. They join Federer and Djokovic as the latest stars to withdraw.
Novak Djokovic plans to make his return for the U.S. Open on Aug. 30 in New York, where he will look to win his 21st career major and a calendar Grand Slam.