Djokovic had made the Olympic gold medal in singles one of his big priorities for 2016. He could not make it past the first round, and when it was over, both he and his conqueror, Juan Martín del Potro, were in tears in Rio de Janeiro.

In a raucous atmosphere on center court at the Olympic Tennis Center, Del Potro produced one of the most remarkable performances of his career: upsetting Djokovic, 7-6 (4), 7-6 (2).

The Williamses lost, 6-3, 6-4, to the Czech team of Barbora Strycova and Lucie Safarova.

The defeat was the Williams sisters’ first loss playing together at the Olympics. They won the gold medal in 2000, 2008 and 2012, and Sunday’s surprise defeat came against a team that had never won a match together.

— CHRISTOPHER CLAREY

The Medals, So Far