In-form world number five Victoria Azarenka has withdrawn from the Madrid Open due to a back injury.
The former world number one has returned to the peak of her powers this year, winning three titles to raise hopes she can add to her tally of two grand-slam titles.
Azarenka beat Alize Cornet in Madrid to stretch her winning run to 16 matches on the WTA Tour and in the Fed Cup.
But the fourth seed will not be winning a third title in a row this weekend after suffering an injury blow which forced her to pull out of her second-round match against Louisa Chirico.
The 26-year-old from Belarus revealed that she tweaked her lower back during a 6-3 6-2 victory over Cornet on Monday,
Azarenka won the Miami Open last month after beating Serena Williams to be crowned champion at Indian Wells.