Alex de Minaur withstood an Ugo Humbert barrage, running away with an impressive comeback win to complete his ATP Cup campaign with Australia already out at the group stage. 

The Australian faced a break point at 4-4 in the second set but charged forward to secure a 3-6 7-6 (7-2) 6-1 win in Sydney on Thursday night.

Fellow rising star Humbert looked almost untouchable before that crucial moment, leaning on his whipping left-handed forehand to control proceedings.

But de Minaur raced through the tie-break before prevailing in a memorable 36-shot rally to break Humbert's serve in the deciding set.

"The Demon" was at it again on match point, somehow reaching a wide backhand before sprinting forward to dig out a forehand and force the error. The Australian men's number one wagged his finger and mouthed "not here" as he walked to the net to shake hands with his defeated opponent.

The victory followed de Minaur's defeat of world number seven Matteo Berrettini of Italy earlier in the ATP Cup before he was humbled by US Open champion Daniil Medvedev, who has led Russia to a semi-final clash against Canada.

"Stay in there (was key); Ugo was playing some unbelievable tennis," de Minaur said.

"He's a very high-level player — beat Medvedev on this court — but I just had to stick in there and get the crowd going.

"I got that second set and I just had that energy to keep on going."

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De Minaur's victory followed a frustrating loss for fellow Aussie James Duckworth, who fell 6-4 7-6 (8-6) to French up-and-comer Arthur Rinderknech.

Rising into the world's top 50 for the first time, Duckworth arrived confident after earning his place in Lleyton Hewitt's Australian outfit.

But he missed the country's opening clash against Italy with hip soreness, then lost both matches against Russia as the hosts failed to make the semi-final stage.

It rendered their final tie against France a dead rubber, with defending champions Russia assured the group's only spot in the semi-finals. The other semi-final will be played between Spain and Poland.

Happy with his form and health after COVID-19 slowed his 2021, de Minaur is set to withdraw from the Sydney Tennis Classic and head straight to Melbourne for the Australian Open.

"It's (the ATP Cup) a special event, we played some great tennis but it didn't go our way," he said.

"I'm feeling great, playing some great tennis, feeling in best shape of my career.

"I'll see what I can do, head to Melbourne and hopefully put on a show."

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Elsewhere, Rafael Nadal has enjoyed a quiet win over Ricardas Berankis at the Melbourne Summer Set, cruising through to the quarter-final after a 6-2 7-5 win in his first ATP tour match since August.

The win came after Nadal commented on the unfolding situation with rival Novak Djokovic, with whom he shares 20 grand slam wins.

The Australian Open could determine the all-time men's singles leader after Roger Federer withdrew from this year's event due to injury.

Defending Australian Open champion Naomi Osaka also secured a comfortable win at the Melbourne warm-up event, defeating Maryna Zanevska 6-1 6-1.

It was Osaka's first match since losing the third round of the US Open in September.

AAP/ABC Sport