CHARLESTON, S.C. (AP) -- Serena Williams is through to the Family Circle Cup semifinals and waits to see if Venus can do the same.
Fifth-seeded Serena Williams advanced on Friday when 22-year-old Sabine Lisicki retired in the first set after rolling her ankle and falling to the court. Lisicki received treatment and played three more games before withdrawing in tears.
Serena Williams comforted her opponent on the sideline and applauded with the stadium crowd as Lisicki, the 2009 champion her, left.
"I told her, `Don't cry. You're going to make me cry, too,"' said Serena, this tournament's 2008 champion who is ranked No. 10.
Lisicki, the sixth seed, went to the hospital to have an MRI test on her left ankle.
Williams has had her share of injuries that forced her to miss major tournaments. She told the young German that she had time to heal and would be back.
"I said, `It's OK. It's not the French Open. You've got time to get better."'
Williams might not have much time before the latest clash of Williams-vs.-Williams.
First, Venus has to get past reigning U.S. Open champion Samantha Stosur in a later quarterfinal Friday. Stosur completed her rain-delayed, third-round match earlier in the day, needing three sets to get past Galina Voskoboeva 6-3, 4-6, 6-2.
Should Venus prevail, it would again set up one of the most captivating rivalries in women's tennis. The sisters haven't played since the WTA Championships in 2009. Serena said neither would hold back because both are eager to add a second Family Circle title to their resume.
"I think it'll be great, I really do," Serena Williams said. "Obviously, I want to win and she really wants to win."
Venus Williams won this title in 2004. This is her second tournament since she was diagnosed with Sjogren's syndrome, a fatigue-inducing autoimmune disease that forced her to withdraw from the U.S. Open last summer. Venus returned to tennis last month and advanced to the quarterfinals of the Sony Ericsson Open before losing to eventual champion Agnieszka Radwanska. Venus hasn't dropped a set in three matches so far despite this being her first tournament on clay since 2010.
Serena expects the competitive juices each have shown in winning a combined 20 grand slam singles titles - Serena has 13, Venus seven - to show front and center if the two meet up Saturday. Serena leads the sibling rivalry, 13-10. The two have split their two previous matches on clay, the last one coming in Serena's 2002 French Open championship - the only time Serena has won at Roand Garros.
"Venus is an excellent clay-court player," Serena said. "And I'm pretty decent on clay."
Facing Stosur won't be easy for Venus, despite Williams' 4-0 record in their meetings. Stosur is ranked fifth in the world and relentless in attacking the ball.
Venus said Thursday that Stosur is one of the power players who do well on clay. "So it's an interesting mix," Williams said.
Also, No. 4 seed Vera Zvonareva takes on ninth-seeded Lucie Safarova, and No. 13 seed Nadia Petrova faces 14th-seeded Polona Hercog in later quarterfinals. Petrova is the 2006 Family Circle champion.