PARIS, France - Quarterfinal debutante Agnieszka Radwanska takes on clay court queen Sara Errani first up on Philippe Chatrier, while over on Suzanne Lenglen Serena Williams faces Svetlana Kuznetsova in the battle of former champions.
Court Philippe Chatrier
 Agnieszka Radwanska (POL #4) vs.  Sara Errani (ITA #5)
Head-to-head: Radwanska leads 6-1
Sara Errani has long since proved that last year's run to the final was a breakthrough, rather than a one-off, cementing a place at the top of the game with her unique brand of all-court counterpunching. Coming into Roland Garros, only Serena Williams had won more matches this year than Errani, who has already racked up 35 thanks to the successful defense of her Acapulco title and another solid showing on the European clay.
If she is to make it through to another semifinal here, though, she will have to figure out the riddle that is Agnieszka Radwanska. In seven previous encounters, the Pole has won six, including a handful of times on Errani's beloved clay.
After an up-and-down showing against big-hitting German qualifier Dinah Pfizenmaier in the third round, Radwanska really clicked into gear against Ana Ivanovic last time out, exhibiting her full repertoire of shots in a surprisingly comfortable straight set victory.
Despite her previous struggles, Errani can take comfort from the pair's last meeting, when she adopted an uncharacteristically aggressive game plan and came within a handful of points of victory during a three-hour thriller at last year's WTA Championships.
Court Suzanne Lenglen
 Serena Williams (USA #1) vs. Svetlana Kuznetsova (RUS #39)
Head-to-head: Williams leads 6-2
In her four matches in Paris thus far, Serena Williams has dropped a meager 10 games, spending just 244 minutes on court. In fact, the only thing that has not been fluent is the ever-improving French she is using to converse with during the post-match interviews.
Her stroll into the quarterfinals takes her current win streak to 28 matches - the most since Justine Henin's 32 on the spin between 2007 and 2008 - and 23 sets. Daunting numbers. Particularly for Svetlana Kuznetsova, who is the next player charged with derailing the Williams juggernaut.
However, unlike Anna Tatishvili, Caroline Garcia, Sorana Cirstea and Roberta Vinci, Kuznetsova has defeated Williams before. Twice, in fact, with one of these wins coming on her way to the French Open title in 2009.
At her best, of which there have been glimpses in the opening rounds, the Russian has the movement, touch and shotmaking to live with Williams. To topple Williams, glimpses will not be enough, and she will have to maintain - and possibly surpass - this level for three potentially grueling sets.