Victoria Azarenka retires from Madrid Open with back injury

MADRID - Fourth-seeded Victoria Azarenka has pulled out of the Madrid Open because of a back injury.

The 26-year-old Azarenka says she ''tweaked'' her back during her opening match against Laura Robson and that the pain persisted during her second-round win over Alize Cornet.

Azarenka had been scheduled to play Louisa Chirico of the United States on Wednesday, but she withdrew during the warmups.

Azarenka says ''I don't feel that I'm able to compete today,'' adding she will undergo medical tests in Madrid later Wednesday before making a decision about playing in Rome.

She says it is going to be a matter of making the ''smart decision.''