Ironman Alex de Minaur is a surprising late addition in a mighty boost to Australia's Davis Cup quarterfinal hopes in Malaga.

De Minaur was not listed in Australia's initial team to face the USA on Thursday night before the world number nine declared his availability after a "special" practice session with retiring legend Rafael Nadal.

After a gruelling but triumphant season dogged by a hip injury, it had been expected that de Minaur would sit out the Cup finals after losing all three of his matches at last week's ATP Finals in Turin.

"Look, I'm very happy to be back here. Obviously it's been a tough year with injuries, but I am feeling a lot better and I'm feeling quite fit and ready to compete," he said.

"So obviously if my body was holding up, I was always going to put my hand up and be ready to come here and play for Australia."

De Minaur is sure to be extra inspired when he hits the court on Thursday.

After becoming the first Australian since now-Cup captain Lleyton Hewitt in 2005 to reach three consecutive grand slam quarterfinals, the 25-year-old had the honour of hitting with Nadal ahead of the former world number one's final tournament this week.

"It was a special moment for sure," de Minaur said.

"I have been fortunate enough to share the court with Rafa a couple times, and I have hit with him a couple times, but it's always extra special, this potentially being the last dance.

"So it was good to get one last hit with him."

Team USA boast a formidable line-up led by 2024 US Open runner-up and world number five Taylor Fritz and fellow top-20 stars Tommy Paul and Ben Shelton.

But de Minaur and world number 24 Alexei Popyrin, still riding high after winning the Montreal Masters 1000 crown then toppling Novak Djokovic at Flushing Meadows, hope to have the fans' backing at the Malaga indoor arena.

The Sydney-born pair grew up together in Alacante after their parents felt Spain was the best country to advance their tennis careers.

"It's always great to come back here to Malaga. We have had a pretty good connection with the crowd throughout the years," de Minaur said.

"It's of course an away tie for us, but we are going to do our best to get the Spanish crowd to support us, because we've got some Spanish roots. So hopefully we can pull on that."

Runners-up last year to Italy, the Australians — also featuring world No.28 Jordan Thompson, Thanasi Kokkinakis and Olympic doubles gold medallist Matt Ebden — could meet Jannik Sinner's team in the semi-finals.

The defending champions face Argentina in their quarter-final on Thursday.

"We have had tough matches the last couple of years here and have been able to dig deep and find a way to get through to the final," Hewitt said.

"We're going to have to do that again on Thursday."

Australia haven't won the Davis Cup since 2003 in Melbourne and Hewitt hopes next year's finals will be staged Down Under.

"We'd really like to hopefully host the finals as well. We'd like to get the opportunity to put a bid in for next year," he said.

"I think we deserve that. I have been working extremely hard with the (International Tennis) Federation to be able to give us that opportunity.

"It's frustrating for these guys to always have to come all the way over to Europe every single year to play in the finals.

"I know how special it was for me to win Davis Cup finals in Australia. We all know how good a tradition our country has in this competition for well over a 100 years. We'll see where that lands."