Serena Williams and Garbine Muguruza were knocked out of the women's singles competition in the third round on a dramatic day of tennis at Rio 2016 on Tuesday.
Williams was the defending champion having won gold in London four years ago, while Spanish third seed Muguruza ranked among the favourites in Brazil following her French Open triumph earlier this year.
But 22-time grand-slam champion Williams, seemingly bothered by a shoulder injury, went down 6-4 6-3 to Elina Svitolina at the Olympic Tennis Centre.
Muguruza, meanwhile, was thumped 6-1 6-1 by Monica Puig, leaving only two of the top eight seeds - Angelique Kerber (2) and Madison Keys (7) - left in the draw.
The men's competition stuck closer to the script, with 2012 champion Andy Murray safely into the third round with a win over Juan Monaco, while Spain's Rafael Nadal also made it through.
Muguruza fared better in the women's doubles, progressing to the quarter-finals with Carla Suarez Navarro following a victory over Kirsten Flipkens and Yanina Wickmayer of Belgium.
There was further success for Spain in the men's doubles, with Nadal and partner Marc Lopez advancing to the semi-finals.
MATCH OF THE DAY
Williams produced 37 unforced errors and was visibly emotional in the latter stages as she lost in one hour and 12 minutes to world number 20 Svitolina.
QUOTES OF THE DAY
"It's obviously disappointing but, you know, she played really well and I think the better player today won," - Williams gracious in defeat.
"I'm over it. This is the Olympic Games, I know it's frustrating and disappointing to lose, but it's my first Games, I was not expecting to come here and win a gold medal like that. So that's all I can say," - Muguruza ready to move on from singles loss.
"You know, two months without competing I don't expect much. I just expect to enjoy the Olympic experience again and that's what I'm doing," - Nadal enjoying every minute of his Olympic experience after missing out through injury in 2012.
Nadal and Muguruza team up for the mixed doubles on Wednesday, with the former also taking on Gilles Simon in the singles.
Murray takes on Fabio Fognini for a place in the men's quarters, while Svitolina's reward is a last-eight clash with 11th seed Petra Kvitova.