Top-seeded Agnieszka Radwanska has withdrawn from the Family Circle Cup because of a back injury.
Radwanska, ranked No. 4, defeated Maria Sharapova on Saturday in the final of the Sony Ericsson Open in Miami.
The Family Circle Cup announced that Radwanska's departure ends the possibility that Venus and Serena Williams can meet in the Easter Sunday finals of the $740,000 WTA Family Circle event on the green clay on Daniel Island.
The seeded players must be repositioned, and the Williams sisters are now in the same side of the draw and can meet only in the semifinals.