A day of shocks in the Rio 2016 tennis tournaments saw world number one Novak Djokovic beaten in the first round of the men's singles by Juan Martin Del Potro as the Williams and Murray siblings suffered doubles losses.
Seeking to bounce back from his surprise early exit at Wimbledon last month, Djokovic went down in two tie-breaks to Del Potro, whose forehand proved particularly devastating.
The top seed was in tears as he departed Centre Court and went on to state the result represented one of the toughest losses of his career.
Both Serena Williams and Andy Murray made it safely through their first-round singles matches, against Daria Gavrilova and Viktor Troicki respectively, while there were also wins for Spain's Rafael Nadal and Garbine Muguruza.
However, the Williams sisters and Murray brothers bowed out of the respective women's and men's doubles competitions - the former losing their perfect Olympic record in the process.
Serena and Venus fell victim to the Czech pairing of Barbora Strycova and Lucie Safarova. Andy and Jamie Murray lost 7-6 (8-6) 7-6 (16-14) to home favourites Thomaz Bellucci and Andre Sa.
The top seeds in the men's doubles, Pierre-Hugues Herbert and Nicolas Mahut of France, also bowed out courtesy of a straight-sets reversal at the hands of Colombia's Robert Farah and Juan-Sebastain Cabal.
MATCH OF THE DAY
Djokovic went down under a hail of Del Potro winners, the Argentinian's forehand proving particularly devastating as he overcame the top seed in style.
"If this was not the Olympic Games I would not be here competing because I need to have more rehab," Nadal makes reference to his wrist injury after easing past Federico Delbonis.
"I'm very sad and disappointed from my side to go out in a tournament this early, but on the other hand I'm glad a good friend of mine, and somebody who has struggled the last couple of years with injuries, is back and playing at this level," Djokovic pays gracious tribute to the fit-again Del Potro, whose career has been severely hampered by wrist injuries.
Serena Williams, Angelique Kerber and Garbine Muguruza are among those in singles action on Monday, while Djokovic will hope for better fortunes when he teams up with 40-year-old Nenad Zimonjic in round two of the men's doubles.