A rousing comeback saw John Millman stun Thiago Seyboth Wild to give an Australian team missing Nick Kyrgios a 2-0 lead over Brazil in their Davis Cup qualifier on Friday.
With a slot in the Madrid finals at stake, Jordan Thompson put the home team on the front foot in the opening singles, beating the experienced Thiago Monterio 6-4, 6-4 at Adelaide's Memorial Drive.
It looked like the visitors would strike back in the second rubber as rising star Seyboth Wild, who won his first ATP title in Chile last week, served for the match at 5-4 against Millman.
But the Australian, cheered on by a patriotic crowd, broke back and took the second set in a tiebreaker before running away with the third to post a gutsy 4-6, 7-6 (7/0), 6-2 win.
"I think I showed a bit of grit out there," said Millman. "I used the bench, the team and I soaked up the experience of (captain) Lleyton (Hewitt) and Rochey (coach Tony Roche).
"That's what Davis Cup is all about, never giving up."
Earlier Thompson, who improved his Davis Cup record to 7-4, ensured Australia started on a winning note.
The opening set went with serve until he lifted his intensity to convert on his first set point with the help of a netted forehand.
He carried the momentum into the second as Monterio's error count mounted, racing to a 4-1 lead before his focus lapsed and the Brazilian roared back to 4-4.
But it was ultimately Thompson's day, with another break in the 10th game handing him victory.
"It was just a really solid match," he said. "I'm really pleased with the result and the performance."
Hewitt's team is without Kyrgios who is dealing with a wrist injury that forced him to retire in Acapulco last month, while Alex De Minaur was a late withdrawal as he struggles to get over an abdominal tear.
Alex Bolt and John Peers were called up instead with the doubles and reverse singles on Saturday.
The winner of the tie will join 11 other qualifiers and the 2019 semi-finalists - Canada, Britain, Russia and Spain - along with wildcards France and Serbia in the Davis Cup finals in Spain in November.
Results Friday on the opening day of Australia's Davis Cup qualifying tie against Brazil at Adelaide's Memorial Drive:
Australia 2 Brazil 0
Jordan Thompson (AUS) bt Thiago Monteiro (BRA) 6-4, 6-4
John Millman (AUS) bt Thiago Seyboth Wild (BRA) 4-6, 7-6 (7/0), 6-2
James Duckworth/John Peers (AUS) v Marcelo Demoliner/Felipe Meligeni Rodrigues Alves (BRA)
John Millman (AUS) v Thiago Monteiro (BRA)
Jordan Thompson (AUS) v Thiago Seyboth Wild (BRA)