Qualifiers Bigi and Tosta produced the shock of the day in the Russian city when they stunned second seeds and reigning world champions Sarah Pavan and Melissa Humana-Paredes of Canada 17-21, 21-19, 15-8.

And the duo almost pulled off another surprise as they took the opening set against Huberli and Betschart.

But the Swiss pair, who had beaten Americans Brooke Sweat and Kerri Walsh Jennings in their first Pool B match 21-12, 21-19, came roaring back to complete a 14-21, 21-14, 15-9 triumph.

Pavan and Humana-Paredes responded from their defeat to Bigi and Tosta by seeing off Sweat and three-time Olympic gold medallist Walsh Jennings 21-17, 16-21, 15-9.

Sarah Sponcil and Kelly Claes - Sweat and Walsh Jennings’ main rivals for one of the United States’ Olympic berths for Tokyo 2020, cruised through Pool C without dropping a set.

The pair claimed a 21-12, 21-18 victory over Italy’s Marta Menegatti and Viktoria Orsi Toth and a 21-15, 22-20 triumph against Brazilian third seeds Agatha Bednarczuk and Eduarda Santos Lisboa.

Heather Bansley and Brandie Wilkerson of Canada produced two dominant displays in Pool D as the 20th seeds saw off Germany’s Karla Borger and Julia Sude and Brazil’s Taiana Lima and Talita Antunes in straight sets.

Victoria Bieneck and Isabel Schneider, seeded 21st, also upset two teams above them in the seeding.

The Germans achieved a tie-breaker victory in their first Pool E match, overcoming 12th seeds Emily Stockman and Kelley Kolinske 23-21, 18-21, 15-10 before delivering a 21-11, 21-12 win over Swiss fifth seeds Joana Heidrich and Anouk Verge-Depre.

Brazil’s Barbara Seixas and Carol Solberg lost the first set of a mouth-watering Pool F battle against Americans Alix Klineman and April Ross before battling back to claim a 17-21, 21-17, 15-5 victory.

There were no major surprises in the rest of the pools as top-seeded Nadezda Makroguzova and Svetlana Kholomina of Russia, Margareta Kozuch and Laura Ludwig of Germany and Sanne Keizer and Madelein Meppelink of The Netherlands won Pools A, G and H respectively.

Sixteen men’s teams secured their spots among the last 24 in the single elimination rounds in Sochi by winning their first pool matches today.

Italy’s Paolo Nicolai and Daniele Lupo overcame Spaniards Pablo Herrera and Adrian Gavira 14-21, 21-18, 15-11 to set up a meeting with Qatari fourth seeds Cherif Younousse and Ahmed Tijan for the top of the standings in Pool D.

Americans Jake Gibb and Taylor Crabb were very close to achieving a similar against Robin Seidl and Philipp Waller as they created a match-point opportunity only for the Austrian qualifiers to celebrate a 21-14, 20-22, 17-15 win.

Seidl and Waller will contest the Pool F pole position with Italy’s Adrian Carambula and Enrico Rossi.

Tri Bourne and Trevor Crabb of the US snatched a 21-19, 18-21, 15-10 victory over Germany’s Nils Ehlers and Lars Fluggen to move to a Pool A final encounter with Russian world champions and top seeds Viacheslav Krasilnikov and Oleg Stoyanovskiy.

Norway’s Anders Mol and Christian Sorum and Poland’s Piotr Kantor and Bartosz Losiak set up a meeting for the first place in Pool B.

Dutch duo Christiaan Varenhorst and Steven van de Velde will be challenged by main draw newcomers Daniil Kuvichka and Anton Kislytsyn of Russia for the top of Pool C.

Ondrej Perusic and David Schweiner of the Czech Republic and Americans Nick Lucena and Phil Dalhausser will go against each other in the Pool E winners match.

Reigning Olympic champion Alison Cerutti and Alvaro Filho of Brazil will take on Switzerland’s Adrian Heidrich and Mirco Gerson in Pool G, while the top of Pool H will be resolved in an encounter between Latvia’s Martins Plavins and Edgars Tocs and Russia’s Konstantin Semenov and Ilya Leshukov.