Daniil Medvedev suffered a surprise three-set defeat to Ugo Humbert ©Getty Images

Reigning champions Russia bounced back from world number two Daniil Medvedev’s shock singles loss to defeat France at the Association of Tennis Professionals (ATP) Cup in Sydney in Australia.

Ugo Humbert trailed Medvedev by a set and 3-0 before storming back to claim a stunning 6-7, 7-5, 7-6 victory to put France in front in the Group B opener.

World number 167 Roman Safiullin then stepped up to the plate as he downed Arthur Rinderknech 2-6, 7-5, 6-3 in the second singles match before helping Russia beat France in the doubles.

Safiullin teamed up with Medvedev as they defeated Fabrice Martin and Edouard Roger-Vasselin 6-4, 6-4.

The 24-year-old was given the opportunity to represent Russia after Andrey Rublev and Aslan Karatsev both tested positive for coronavirus.

John Peers and Luke Saville completed a comeback 2-1 victory for Australia over Italy.

The pair downed Matteo Berrettini and Simone Bolelli 6-3, 7-5 as the host nation got their campaign off to winning start in Group B.

Alex de Minaur lifted the roof off the Ken Rosewall Arena when he kept alive Australia's opening-tie hopes with a 6-3, 7-6 win over world number seven Berrettini.

Jannik Sinner had produced a comprehensive performance on his ATP Cup debut to give Italy a 1-0 lead with a 6-1, 6-3 thrashing of Max Purcell.

The United States saw off Canada 3-0 thanks to victories for Taylor Fritz and John Isner in Group C.

Isner made a quick start for the US when he thumped Brayden Schnur 6-1, 6-4 in 66 minutes.

Fritz let slip four set points in the opening-set tiebreak but recovered to defeat Felix Auger-Aliassime 6-7, 6-4, 6-4.

Canada called upon Schnur after Denis Shapovalov withdrew from his opening singles match of the season "due to fatigue", according to the ATP.

Shapovalov, who tested positive for COVID-19 upon his arrival in Sydney, took to the court later alongside Auger-Aliassime but lost 6-4, 6-4 to Fritz and Isner.

"I'm disappointed not to be able to play the first match, but I just didn’t feel ready physically yet, so we did what is best for the team," Shapovalov said.

Dan Evans inspired Britain to a 2-1 victory over Germany as he won two matches including a deciding doubles encounter with Jamie Murray in Group C.

Evans beat Jan-Lennard Struff 6-1, 6-2 following Alexander Zverev’s 7-6, 6-1 triumph against Cameron Norrie before partnering Murray to a 6-3, 6-4 success over Kevin Krawietz and Zverev.

Action continues tomorrow with Poland facing Georgia and Greece taking on Argentina in Group D.

Norway come up against Spain and Serbia tackle Chile in Group A.