Top-seeded Serena Williams withdrew from the Western & Southern Open in Cincinnati with a shoulder injury, the tournament officials announced.
Williams is tournament’s two-time defending champion dropped of the tournament on Monday following a morning practice session.
Williams was set to participate in the tournament after being beaten in the first round of the Olympic singles tournament. The men's No. 1 player, Novak Djokovic also withdrew from the Western & Southern Open, citing a wrist injury.
The withdrawal gives No. 2 seed Angelique Kerber a chance to earn the world's top spot if she can when the tournament championship.