Competition wide open - Beach Volleyball
Horse Guards Parade was the scene of a huge upset as reigning Olympic Games champions Todd Rogers and Phil Dalhausser of the USA crashed out of the men's Beach Volleyball competition.
Italians Paolo Nicolai and Daniele Lupo only reached the knockout stage by virtue of winning a Lucky Loser play-off against Canada, having finished third in Pool A after one win and two losses.
But they served up by far the biggest win of their careers as they prevailed in straight sets against the Beijing 2008 gold medallists, 21-17 21-19.
At 23 and 21 respectively, Nicolai and Lupo are the youngest team at the Games, but they defied their youth to produce a performance heavy on both powerful attack shots and improvised dinks.
In the form of the tall Nicolai, they also boast one of the standout blockers at the tournament, and he was at the top of his game as he repeatedly denied USA's Rogers and Dalhausser's kill shots.
Italy's win must rank as one of the biggest surprises in the sport at Olympic Games level, with the experienced Rogers and Dalhausser 23-time winners on the World Tour, while Nicolai and Lupo's best result came with a second place in Beijing earlier this year.
The USA's shock defeat looks to have opened the way for the Brazilians, Ricardo Santos and Pedro Cunha, who showed all the weapons in their formidable armoury as they saw off the challenge of a strong Spanish team to reach the last eight, 2-0.
The Spanish pair of Pablo Herrera and Adrian Gavira looked in good form during the preliminary phase but had no answers as the Brazilians, among the favourites for gold, posted a 21-18 21-19 win.
Brazil's second-ranked team have reached the quarter-finals without dropping a set, with their perfect record owing much to the imperious form of 37-year-old Ricardo, who is bidding for a fourth Olympic Games medal.
Elsewhere in the men's competition, Poland's Grzegorz Fijalek and Mariusz Prudel booked their place in the quarter-finals after prevailing 21-18 21-17 in the early encounter over Switzerland's Sascha Heyer and Seba Chevallier.
Latvia's Martins Plavins and Janis Smedins also eased into the last eight with a straight-sets dismissal of Norway's Tarjei Viken Skarlund and Martin Spinnangr.
The women's competition is shaping up to be equally enthralling, with Germany having already been guaranteed a place in the last eight as Sara Goller and Laura Ludwig became the first pair to reach the quarter-finals with a routine win over their countrywomen Katrin Holtwick and Ilka Semmler.
Jennifer Kessy and April Ross of the USA also saw off the stern challenge of Switzerland's Simone Kuhn and Nadine Zumkehr to seal their progress, before
Austria's Doris and Stefanie Schwaiger earned a repeat of their quarter-final berth at Beijing 2008 as they defeated Anastasia Vasina and Anna Vozakova of Russia.