PHOTO GALLERY: Saturday at the London Olympics

United States' Michael Phelps, right, swims in the men's 4x100-meter medley relay final Saturday at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. Phelps pushed the United States in front to win the medley relay. He leaves the sport with a record 18 golds and 22 medals overall.   |  Mark J. Terrill/The Associated Press

United States' men's 4x100-meter medley relay team Matthew Grevers, left, Michael Phelps and Brendan Hansen shake hands with teammate Nathan Adrian after winning the gold medal Saturday at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London.   |  Matt Slocum/The Associated Press

United States swimmer Michael Phelps acknowledges fans after winning a gold medal in the men's 4x100-meter medley relay Saturday at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London.   |  Jae C. Hong/The Associated Press

United States' Serena Williams returns a shot to Maria Sharapova of Russia in the women's singles gold medal match Saturday at the All England Lawn Tennis Club at Wimbledon, in London, at the 2012 Summer Olympics.   |  Victor R. Caivano/The Associated Press

Gold medalist Serena Williams shows her medal to fans after the medal ceremony Saturday of the women's singles final match at the All England Lawn Tennis Club at Wimbledon, in London, at the 2012 Summer Olympics.   |  Victor R. Caivano/The Associated Press

Team USA's Lebron James, left, and Andre Iguodala celebrate Saturday during a preliminary men's basketball game against Lithuania at the 2012 Summer Olympics in London.   |  Eric Gay/The Associated Press

South Africa's Oscar Pistorius competes Saturday in a men's 400-meter heat in the Olympic Stadium at the 2012 Summer Olympics in London.   |  Matt Dunham/The Associated Press

Britain's Mo Farah, right, Ethiopia's Tariku Bekele, center, and United States' Galen Rupp, left, head for the finish line in the men's 10,000-meter final Saturday in the Olympic Stadium at the 2012 Summer Olympics in London.   |  Anja Niedringhaus/The Associated Press

United States' swimmer Michael Phelps holds up a silver trophy after being honored Saturday as the most-decorated Olympian at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London.   |  Matt Slocum/The Associated Press