Maria Sharapova battles past Marion Bartoli in U.S. Open quarterfinals . The Russian has won all four of her matches against the world She will face world No . 1 ` A quarterfinal with your best friend is difficult , '' Errani said . Victoria Azarenka , who beat her in Australian Open final . Olympic champion Serena Williams will play Sara Errani in the other semifinal .
Maria Sharapova battles past Marion Bartoli in U.S. Open quarterfinals . The Russian has won all four of her matches against the world She will face world No . 1 Victoria Azarenka , who beat her in Australian Open final . Olympic champion Serena Williams will play Sara Errani in the other semifinal .