Serena Williams into the quarterfinals of WTA tournament in Miami . Williams avenges 2011 U.S. Open defeat to Samantha Stosur . World No . 1 Victoria Azarenka fights back to extend 2012 season with win over Maria Sharapova at Australian Open. Venus Williams , Maria Sharapova , Caroline Wozniacki , Li Na also progress .
Serena Williams into the quarterfinals of WTA tournament in Miami . Williams avenges 2011 U.S. Open defeat to Samantha Stosur . World No . 1 Victoria Azarenka fights back to extend 2012 run to 26-0 . Venus Williams , Maria Sharapova , Caroline Wozniacki , Li Na also progress .