Defending champion Serena Williams is out of the Olympics after losing to Ukrainian Elina Svitolina in the women's singles third round.
Williams lost 6-4 6-3 to Svitolina, ranked 20th in the world.
The world number one double faulted five times in the seventh game of the second set to highlight her struggles.
Williams and sister Venus were knocked out of the women's doubles on Sunday when they lost to Czech Republic pair Lucie Safarova and Barbora Strycova.
More to follow.