Tomas Machac beat Jordan Thompson 6-4 7-5 to give three-time champions Czech Republic a 1-0 lead in their Davis Cup quarterfinal against 2022 runners-up Australia on Wednesday.
The Czechs, who arrived at the Finals with a 9-0 win-loss record from three Group Stage ties in September, are aiming to secure a first victory over Australia since 1975.
Their No 2 player Machac backed up an early break with a comfortable service game and withstood a strong fightback from Thompson at 5-4 in the opening set.
There was little to separate the hard-hitting pair in the second set up to 4-4 and Machac traded breaks with his opponent before edging ahead to seal the victory with a forehand winner.
Jiri Lehecka can clinch the tie for the Czechs when he takes on Alex de Minaur later.
The doubles pair of Jakub Mensik and Adam Pavlasek will face Matthew Ebden and Max Purcell if the best-of-three tie goes to a decider.
Australia are without Thanasi Kokkinakis, who was forced to withdraw from the Finals with an ankle injury.
Lleyton Hewitt's side, who lost to Canada in the final last year, are looking to capture the premier men's team competition crown for a 29th time and inch closer to the United States who are top of the pile with 32 titles.