Murray brothers and Williams sisters suffer shock defeats in Rio as doubles dreams end
Second seeds Andy and Jamie Murray crashed out of the men's doubles in the first round after losing a thrilling contest to the Brazilian duo of Andre Sa and Thomaz Bellucci.
The British pair saved six match points during a second set tie-break but were eventually undone by a Bellucci winner which was aided by a net cord and sealed a 7-6 (8/6) 7-6 (16/14) victory in two hours and two minutes.
The shock result means the top two seeds in both doubles competitions have already been eliminated, with top seeds Nicolas Mahut and Pierre Hugues-Herbert of France having lost to Colombia's Juan Sebastian Cabal and Robert Farah.
Three-time champions Serena and Venus Williams suffered their first ever Olympic doubles loss to Czech pair Barbora Strycova and Lucie Safarova, while second seeds Kristina Mladenovic and Caroline Garcia of France were beaten by Japan's Eri Hozumi and Misaki Doi.
After losing the opening set, the Murray brothers broke in the first game of the second thanks to a double fault from Bellucci, but were unable to press home their advantage.
A second tie-break was required and turned into a classic as the British pair recovered from 6-3 down and went on to save three more match points, the fifth conceded by the worst volley Andy has arguably ever hit, but then saved by an ace from the Wimbledon champion.
The 29-year-old then produced a stunning backhand volley from an acute angle to save the sixth match point but could do nothing with the seventh, much to the delight of the partisan home crowd.
Andy said: "You don't get this opportunity very often because the Olympic Games only come around once every four years.
"The way the match went; it was a tough one to lose but it just wasn't meant to be. We saved a lot of match points but we just didn't take our chances."
The two-time Wimbledon champion beat Viktor Troicki earlier in the day in the singles, while Juan Martin Del Potro shocked world number one Novak Djokovic.
"I have to concentrate on the singles now so that is my focus," added the younger Murray brother.
"I have just heard that Novak Djokovic has gone out of the singles. I didn't see the match but that is obviously a surprise.
"I don't think it changes too much for me as I have to just keep my focus and concentrate on one match at a time."
Meanwhile, Defending champions Serena and Venus Williams suffered their first ever Olympic doubles loss in the opening round.
The sisters, who won gold medals in 2000, 2008 and 2012, were beaten 6-3 6-4 by Czech pair Barbora Strycova and Lucie Safarova in a big upset.
Venus finds herself out of the tournament after only two days, unless she decides to play mixed doubles, having lost to Kirsten Flipkens in the opening round of the singles on Saturday night.
The 36-year-old did not speak to the press after that loss, with coach Mary Joe Fernandez revealing Venus was suffering with illness.
She was clearly below her best again in the doubles and Serena, who won her opening singles earlier on Sunday, could not find a high enough level to make up for it.
The world number one said: "It was a really tough match for us, a really tough draw, but we're used to tough draws. We didn't play our best whatsoever tonight. We played terrible and it showed in the result."
For Serena, it was a first ever loss in Olympic doubles. She missed out on Athens in 2004, when Venus suffered a first-round defeat alongside Chanda Rubin.
Both sisters hold four gold medals, making them the most successful Olympic tennis players of all time, and they are rare among their peers in how much they prioritise the Games.
This surely will be an Olympic swansong for both, but Serena, who won double gold in London, insisted the result was not too much of a blow.
"I wouldn't say it's devastating," she said. "We had a chance to compete for our country and we did the best that we can.
"We had a blast out there. It was a lot of fun and we'll always remember these moments and these matches, and I think that's what matters most.
"We've had so many Olympic doubles golds, so many grand slam championships. It's been unbelievable."