Williams sisters to face off in Charleston semis

Venus and Serena Williams each won a pair of matches Friday and will face each other in the semifinals at the Family Circle Cup tennis event.

In a rematch of last year's final, the top-seeded Serena upended sixth-seeded Czech Lucie Safarova, 6-4, 6-1. Serena, who beat Safarova in last year's finale, also titled here in 2008 and was the 2003 Family Circle runner-up.

The fifth-seeded former world No. 1 Venus topped fellow American Madison Keys 6-4, 6-4 in her quarterfinal outing on Day 5. Venus was forced to play a pair of matches on Friday after rain postponed her third-round bout on Thursday.

Venus was the Charleston champ back in 2004.

The results set up the 24th meeting between the Williams sisters with Serena holding a 13-10 all-time lead heading into Saturday's clash. They haven't met since the 2009 WTA Tour Championships in Doha, and Serena has won the last four matchups.

Also Friday, second seed Caroline Wozniacki of Denmark was upset by Switzerland's Stefanie Voegele in the quarterfinals, 3-6, 6-4, 6-3.

The former world No. 1 Wozniacki was a runner-up at Indian Wells a few weeks ago, titled on the green clay here at Daniel Island Tennis Center in 2011 and was the Charleston runner-up in 2009.

Another quarterfinal saw ninth-seeded former No. 1 Jelena Jankovic paste Canada's Eugenie Bouchard 6-2, 6-1. Jankovic captured this Family Circle event back in 2007.

Before the quarterfinals were staged on Friday, four third-round matches had to be played. In those outings, Serena whipped fellow American Mallory Burdette 6-4, 6-2; Venus snuck past 12th-seeded compatriot Varvara Lepchenko 6-2, 4-6, 6-2; Safarova subdued 11th-seeded Romanian Sorana Cirstea 6-3, 5-7, 6-1; and Keys cut down fellow countrywoman Bethanie Mattek-Sands 7-6 (7-4), 6-4.

The winner of this $795,000 tournament will earn $125,000.