If I'm not mistaken, she was supposed to be in Vinci's quarter of the draw. Thanks to her withdrawal (and other things) that draw opened up nicely and Vinci reached the semis. In hindsight oh how would Serena have loved to have gotten the free pass called Sharapova (who hits as many doubles in one game as Vinci did in whole match) in the semis instead. Very smart tactics from Sharapova. She stopped Serena from winning all four by doing nothing, something she couldn't have accomplished by playing against Serena.