Former champion Serena Williams was an easy quarterfinal winner Friday at the $740,000 Family Circle Cup tennis event.

The fifth-seeded Williams was handling sixth seed Sabine Lisicki, 4-1 in the first set, when the German retired on the green clay at Family Circle Tennis Center. The capable Lisicki was the Charleston champ in 2009.

The former world No. 1 Williams titled here in 2008 and was the Family Circle runner-up in 2003.

Williams will meet second-seeded Aussie Sam Stosur or her wild card big sister Venus in Saturday's final four. The world No. 10 Serena lost to Stosur in last year's U.S. Open finale. Venus was the 2004 Charleston champ.

Stosur had to complete a rain-suspended third-round match from Thursday, which she did with a 6-3, 4-6, 6-2 victory over Kazakhstan's Galina Voskoboeva on Friday. Stosur led 4-2 in the first set when play was called on Thursday.

This week's winner will earn $115,000.