World No.2 Medvedev led by a set and 3-0 but stumbled from there and went down 6-7 (5-7) 7-5 7-6 (7-2) at the team event in Sydney.

He put that defeat behind him and paired up with Roman Safiullin in doubles to clinch a 2-1 victory for Russia over France in the round-robin Group B tie.

Medvedev and Safiullin were 6-4 6-4 winners over Fabrice Martin and Edouard Roger-Vasselin in the tie decider, with world No.167 Safiullin having earlier scored an impressive 2-6 7-5 6-3 singles victory over Arthur Rinderknech.

Humbert's remarkable comeback victory over Medvedev was the standout result of the contest, however, with the 23-year-old French left hander saying afterwards: "It was a very tough match. I am very happy."

Metz-born Humbert added: "I had some opportunities in the first set and I just tried to stay relaxed and focused on what I had to do. It was a great match."

Australia had an eye-catching win in the same group, landing a 2-1 success over Italy, helped by Alex de Minaur beating Wimbledon runner-up Matteo Berrettini.

De Minaur scored a 6-3 7-6 (7-4) win to level the tie after Jannik Sinner swept past Max Purcell 6-1 6-3, with Berrettini and Simone Bolelli then beaten 6-3 7-5 in a late-night doubles tussle by John Peers and Luke Saville.

In Group C, Great Britain scored a 2-1 win over Germany, with Dan Evans and Jamie Murray teaming up in doubles to beat Alexander Zverev and Kevin Krawietz 6-3 6-4 to take the tie.

Zverev had earlier been too good for Cameron Norrie, posting a 7-6 (7-2) 6-1 win, after Evans sped to a 6-1 6-2 victory over Jan-Lennard Struff.

In their next tie, Germany will do battle with a United States side which was an impressive 3-0 winner against Canada on Sunday. John Isner and Taylor Fritz scored singles victories over Brayden Schnur and Felix Auger-Aliassime before pairing up to beat Auger-Aliassime and Denis Shapovalov in doubles.