World number one Maria Sharapova and Australian Open champion Serena Williams have withdrawn from next week's Dubai Open.
Tournament organisers confirmed that Russian Sharapova had pulled out because of a hamstring injury.
Williams, who won her eighth Grand Slam title with victory over Sharapova in the Melbourne Park final last month, said she is still suffering from the flu that caused her to miss this week's Bangalore Open.
Sharapova sustained her injury in Tokyo this month.
"I tried to do everything possible to be in condition to play in Dubai as it is one of my favourite tournaments, but unfortunately I'm not ready," she said in a statement.
