With a win, Krzyzewski would join Henry Iba (1964, 1968) as the only U.S. coach to lead the Americans to gold medals in consecutive Olympics.
The rest of the Olympic action Saturday:
Jaqueline Carvalho had 18 points and Brazil beat the United States in four sets to stop the Americans from winning their first Olympic gold medal in women's volleyball.
Brazil became the third team to repeat as gold medalist. The Soviet Union won in 1968 and 1972, while Cuba won three straight starting with the 1992 Barcelona Games.
American star Destinee Hooker was held to 14 points.
Castro and Claudino celebrated the victory by leaping into the official's chair, and Brazil's coaches rushed to pile on the other players. Later, the Brazilians danced into the medal ceremony.
Bantamweight Luke Campbell won Britain's first Olympic boxing gold medal in his division since 1908, dramatically knocking down rival John Joe Nevin of Ireland midway through the third round of a 14-11 victory.
China's Zou Shiming, light welterweight Roniel Iglesias, middleweight Ryota Murata and Ukrainian heavyweight Oleksandr Usyk also won their divisions.
Shiming defended his light flyweight gold medal from Beijing with a 13-10 victory over Thailand's Kaeo Pongprayoon, who angrily protested the result.
Iglesias beat Ukraine's Denys Berinchyk 22-15 for Cuba's first boxing gold in London after failing to win gold in Beijing.
Murata narrowly won the second boxing gold in Japan's Olympic history, beating Brazil's Esquiva Falcao 14-13 on the strength of a two-point holding penalty against Falcao in the final round.
Usyk capped the night with a 14-11 gold-medal victory over Clemente Russo of Italy, celebrating with a nimble Cossack dance in the center of the ring.
Tamara Echegoyen, Angela Pumariega and Sofia Toro of Spain won the Olympic gold medal in women's match racing, thanks in part to a boat-handling error by Australia that swept its skipper into the water.
With the best-of-five match tied at one, the boats were sailing nearly side-by-side downwind in the third race in big waves on Weymouth Bay when the Australian crew lost control and its boat rolled on its side. Skipper Olivia Price was swept out of the back of the boat and her crew had to pick her up before continuing.
Spain won that race by 1 minute, 1 second, but the 20-year-old Price and her crew won the fourth race to force a deciding match.
In another mistake, Price was assessed a penalty in Race 5 for a right-of-way violation and Spain sailed ahead to win the gold, leaving the Aussies with the silver.
Britain's Ed McKeever won the men's 200-meter kayak sprint in its Olympic debut, living up to his billing as "Usain Bolt on Water."
McKeever powered his way to victory in 36.246 seconds in front of British Prime Minister David Cameron and his family. Spain's Saul Craviotto Rivero was second and Canada's Mark de Jonge beat France's Maxim Beaumont to bronze by three-hundreths of a second.
Ukraine's Yuri Cheban (men's singles 200-meter canoe sprint) and New Zealand's Lisa Carrington (women's singles 200-meter kayak sprint) also won gold. Yury Postrigay and Alexander Dyachenko of Russia took the men's 200 kayak sprint.
CYCLING - MOUNTAIN BIKE
Julie Bresset picked up the victory at her first Olympics, rolling through the English countryside and waving the French flag as she finished.
Bresset dominated the picturesque course at Hadleigh Farm. She took advantage of a mistake by defending gold medalist Sabine Spitz of Germany to build a massive lead, then rolled through the last of six laps all alone.
The 23-year-old Bresset started blowing kisses to cheering fans on the final straight. Spitz wound up with the silver medal, and Georgia Gould of the United States claimed bronze.
It was only the second Olympic medal in mountain biking for the Americans, who are credited with developing the sport in the 1970s. Susan DeMattei captured bronze at the 1996 Atlanta Games.