Australian second seed Samantha Stosur reached the quarter-finals of the Charleston WTA clay court event on Friday following a 6-3 4-6 6-2 win over Galina Voskoboeva.

Stosur defeated the Kazakh in a match held over from Thursday because of rain, and will now face Venus Williams for a place in the semi-finals.

Serena Williams has already reached the semis, advancing when injury-cursed Sabine Lisicki quit their last-eight clash in floods of tears.

The American fifth seed was 5-1 ahead in the first set when her German opponent, whose career went into a tailspin in 2010 when an injury left her barely able to walk, retired having fallen and injured her ankle.

Williams won warm applause from the crowd as she tried to console the stricken Lisicki.

“I totally get it,” said Williams, who has endured her own battles with injury and illness, when asked if she sympathised with the German.