Australia's Jordan Thompson rallied to beat Tallon Griekspoor of the Netherlands 4-6 7-5 6-3 as the 28-times champions took a 1-0 lead in Tuesday's first quarter-final at the Davis Cup Finals in Malaga.
The duo traded breaks early in the contest before world number 96 Griekspoor gained a foothold to go 4-2 up and the 26-year-old held firm on serve thereafter to take the first set when Thompson sent a backhand wide.
Thompson, ranked 84, was more aggressive in a tighter second set and went 6-5 up with a service hold before breaking a tiring Griekspoor in the next game to drag himself into the contest.
Backed by his Australia teammates and the crowd at the Palacio de Deportes Jose Maria Martin Carpena, the 28-year-old Thompson turned up the heat to establish a comfortable lead and held off a late comeback attempt by his opponent to take the victory on serve.
Alex de Minaur can now secure Australia's place in the semi-finals with a victory over Botic van de Zandschulp in the second singles match.
However, a defeat for the world number 24 will mean the teams will play a deciding doubles rubber where Matthew Ebden and Max Purcell face Dutch pair Wesley Koolhof and Matwe Middelkoop.
The winners of Tuesday's tie will face either six-times champions Spain or Croatia for a place in Sunday's final.
In other quarter-finals, Italy take on the United States while Germany face Canada.