Dinara Safina retires down 5-1 to Victoria Azarenka in Marbella with a possible recurrence of her back injury, which took her out of play much of last season. "Sorry that I had to retire, I felt again my back and got very scared,"  the former No. 1 said on Twitter.  "Just did MRI and CT scan, waiting for the result...I feel so terrible, because today is my father birthday, and I couldn't even finish a match." Azarenka will meet Sara Errani in Saturday's semifinals. - MC