Serena Williams has had to postpone her latest comeback after failing to shake off a foot injury.
The American has not played since winning Wimbledon in July after cutting her foot in a restaurant but has trained in recent weeks with a view to playing in the Generali Ladies Linz event in Austria next week.
But at a final training session in Florida on Saturday she felt the injury once again and pulled out.
Tournament organisers said in a statement: “The tendon injury which has affected her after her Wimbledon victory is still not completely healed and Williams must withdraw.”
Williams will lose her world number one spot when the latest WTA rankings are published today to Caroline Wozniacki.