Track and field starts ; women begin quest for 100-meter title . Phelps , Cavic meet again in 100-meter butterfly final . Soccer quarters feature U.S. against the Football Ferns . Britain 's Andy Murray , who reached Wimbledon finals a few weeks ago , plays Novak Djokovic of Croatia in one men 's singles semifinal . Swimming heats include men vs. women, men vs. men, men vs. women.
Track and field starts ; women begin quest for 100-meter title . Phelps , Cavic meet again in 100-meter butterfly final . Soccer quarters feature U.S. against the Football Ferns . Swimming heats include men vs. women, men vs. men, men vs. women.