Every Friday, after the weekend's matches have been determined, Richard Pagliaro will predict the tournament winners.

Charleston WTA (Semifinal):
Samantha Stosur vs. Serena Williams; Polona Hercog vs. Lucie Safarova

Former Charleston champions face off for a return trip to the final as Serena Williams plays Samantha Stosur in today's first Family Circle Cup semifinal.

It marks the fifth meeting in the last 10 months between two of the WTA's most imposing servers: Williams slammed a career-best 20 aces in a 7-5, 6-3 win over Stosur in Miami last month and Stosur unleashed her helium-high kick serve to stun Williams, 6-2, 6-3, in the 2011 U.S. Open final. Though Williams has won five of eight meetings with Stosur, the Aussie has prevailed in their most meaningful matches. Stosur saved a match point in a dramatic 6-2, 6-7 (2), 8-6 quarterfinal conquest of Williams in the 2010 Roland Garros — their lone clay-court clash — that denied Serena a shot at the single-season Grand Slam.

The second-seeded Stosur was a double winner on Friday, completing a three-set win over Galina Voskoboeva in the morning then returning to court to beat Venus Williams for the first time in five meetings, 6-3, 4-6, 6-3. Stosur is bidding to become the eighth player to beat the Williams sisters at the same tournament and only one woman — Jelena Jankovic, who beat the sisters back-to-back in Rome two years ago — has done it on clay.

The fifth-seeded Serena should be the fresher player: She has not dropped a set and played just five games on Friday before quarterfinal opponent Sabine Lisicki retired with an ankle injury. Stosur is fitter and has the game to stress Serena: She can handcuff Williams up with heavy topspin and force her to hit off her back foot, her kick serve can create timing issues for Williams' typically explosive return game, the former top-ranked doubles player can close at net and the fact she's staved off a match point in beating Williams at the French Open infused her with the confidence to swing freely in the U.S. Open final. Consider Williams has not captured a clay-court title since she beat Vera Zvonareva to win the 2008 Charleston title, only three of her 39 career titles have come on dirt and she looked a bit winded and a half step slow at times losing to another topspin player, Caroline Wozniacki, in Miami last month and you can make a strong case for Stosur as the favorite.

Still, the Charleston clay will give Serena a bit more time to set up for Stosur's shoulder-high shots than the faster Flushing Meadows hard court. Williams knows she must be very active with her feet, take the ball on the rise at times and go at Stosur's forehand early in rally at times to open up space toward her weaker backhand wing and she figures to be highly-motivated to collect her 40th career title. If Williams, who is quicker around the court, is moving well, this may well come down to which woman has the better serving day and I consider Serena's serve the best in the history of women's tennis so I give her the edge.

Polona Hercog crushed former Charleston champion Nadia Petrova, 6-1, 6-2, in the quarterfinals. Hercog surrendered just three games against semifinal opponent Lucie Safarova in their only clay-court meeting at the 2010 French Open. If Hercog reproduces the level of tennis she's shown beating Marion Bartoli and Petrova in succession she can reach the final. But if the left-handed Safarova is landing her forehand she can dictate play from the first strike. Despite her lopsided loss to Hercog in Paris and the fact she can be wildly erratic (see her abysmal first-round loss to Heather Watson in Miami), I think Safarova will navigate a challenging semifinal.

It's not a foregone conclusion the Stosur-Williams winner will take the title — Safarova has won three of five meetings with Stosur — but I'm going all in with Serena.

The Pick: Serena Williams