Serena Williams won't play mixed doubles at the Olympics, and the two U.S. teams will instead feature four doubles specialists - the Bryan brothers, Liezel Huber and Lisa Raymond.
Raymond and Mike Bryan will be reunited after winning Wimbledon this summer, and Huber will play with Bob Bryan.
Williams, who is competing in singles and with her sister Venus in women's doubles, had repeatedly said she also wanted to play mixed doubles. Andy Roddick, John Isner and the Bryans all courted her as a partner.
But she became coy about the subject in recent weeks and wasn't on the list when teams were nominated on Tuesday. Competition begins Wednesday with 16 teams, meaning only two victories are needed to reach the medal round.