Andrea Petkovic has withdrawn from the Family Circle Cup because of a right calf injury, moving second-seeded Caroline Wozniacki into the quarterfinals.
Petkovic was scheduled to play Wozniacki to open Thursday's round of 16. However, she announced in the morning she could not play. Petkovic apologized for pulling out, but felt she might do more damage to her leg if she competed.
Wozniacki, the 2011 Family Circle champion, will play either 10th-seeded Julia Goerges or Stefanie Voegele in the quarterfinals.
Play has been delayed Thursday because of rain in Charleston, South Carolina.