American Venus Williams suffers surprise defeat to German Angelique Kerber . Gold medal favorites Andy Murray and Angelique Kerber progress . Local hero Roger Federer drops first set , recovers to make 24 final . Sharapova advances as she looks for missing gold medal .
Venus Williams suffers surprise defeat to German Angelique Kerber . Gold medal favorites Serena Williams and Roger Federer progress . Local hero Andy Murray drops first set , recovers to make quarter final . Sharapova advances as she looks for missing gold medal .