Inspired captaincy, a nail-biting underdog's win for Thanasi Kokkinakis and good old-fashioned Australian doubles pedigree has powered Australia into the semi-finals of the Davis Cup in Spain.

Lleyton Hewitt outduelled his USA counterpart Bob Bryan in the key captaincy decisions of their quarter-final tie in Malaga on Thursday as Australia defeated the Americans 2-1 in the battle between the two nations who've won the men's 'World Cup of tennis' more than any other.

First, Hewitt plumped for the left-field choice of world No.77 Kokkinakis to open proceedings against big-hitting left-hander Ben Shelton, ranked 21st in the world, and the Aussie outsider came up trumps after saving four match points to prevail in an epic deciding tiebreaker 6-1 4-6 7-6 (16-14).

Then, after Alex de Minaur was blown away 6-4 6-4 by Taylor Fritz in the duel between team's No.1s, it was down to the distinguished doubles grand slam winners Jordan Thompson and Matt Ebden to team up for the first time and defeat Shelton and Tommy Paul 6-4 6-4 in the deciding rubber.

The American skipper Bryan had ditched his specialist doubles pair Rajeev Ram and Austin Krajicek for the decider, deciding to go instead with the power of two of his singles stars - but the decision backfired as they never looked comfortable against the well-grooved Australians.

The win put Hewitt's men one win away from a third-straight appearance in the Davis Cup final after two runner's-up finishes, but they'll first have to get past either champions Italy or Argentina on Saturday (Sunday AEDT).

Led by world No.1 Jannik Sinner, the Italians were launching their defence against the Argentines later on Thursday at the same Jose Maria Martin Carpena indoor arena.

"I don't know if I've been that pumped up in my life. I wanted that for my team," said Kokkinakis, after his amazing win when he finally prevailed on his seventh match point in the marathon 30-point breaker.

"It could have gone either way, but I kept my nerve."

Hewitt had earlier caused surprise by choosing Kokkinakis to lead Australia into battle rather than the higher-ranked Alexei Popyrin and Thompson.

With title glory in Montreal in August, Popyrin was the first Australian since Hewitt in 2003 to win a Masters 1000 crown, before taking down the so-called GOAT Novak Djokovic at the US Open four weeks later.

But Hewitt stuck with Kokkinakis, who was fresh off winning the NSW Open's ATP Challenger Tour event in Sydney after also upsetting 2023 Australian Open runner-up Stefanos Tsitsipas at the US Open in September.

His faith amply rewarded, Hewitt then thrust de Minaur into the second singles for a rematch with world No.4 Fritz, who had pipped the Australian battler at the ATP Finals the previous week.

But 'Demon' never looked near his best, with the US Open runner-up prevailing after just over an hour and 10 minutes.