Dan Evans could not turn the match around, despite the help of GB captain Leon SmithGreat Britain's bid to reach the last eight at the Davis Cup Finals suffered a blow as Dan Evans lost the opening match against the Czech Republic.
With victory in the second group tie enough to see Britain through, Evans was beaten 6-2 7-5 by Tomas Machac.
The Briton led 5-2 in the second set, but lost the momentum he had regained.
Leon Smith's team will still qualify if Cameron Norrie beats Jiri Lehecka, followed by a win for Joe Salisbury and Neal Skupski in the doubles.
Victory over the Czechs in Innsbruck will guarantee Britain - who beat France 2-1 in the best-of-three format on Saturday - a place in the quarter-finals as group winners.
A 3-0 defeat will mean an early exit and a 2-1 defeat would see the group resolved by the percentage of sets won by each team.
Evans' defeat gives Britain work to do
Britain's campaign at the 18-team Davis Cup Finals - which sees group ties held in Innsbruck, Turin and Madrid before the semi-finals and final take place in the Spanish capital - was given the perfect platform by a victory for Evans in Saturday's opening group tie against France.
But he could not replicate that performance as he came up against an inspired Machac, who is ranked 143rd in the world.
Evans said he felt some early nerves in Saturday's match against Adrian Mannarino and the world number 25 made a slow start against 21-year-old Machac, who beat French former world number seven Richard Gasquet on Thursday.
Machac's confidence from that win showed as he broke for a 2-1 lead in the first set, continuing to hit cleanly as he took Evans' serve again for 5-2 and then served out the opener.
The expression of Evans, one of bemusement and shock, showed his concern. The British number two had not played too badly but was overwhelmed by the athletic Machac's stunningly high level.
Evans' frustration boiled over in the first game of the second set, as he broke his racquet by smashing it into the court after being beaten by another passing winner from the Czech.
While that emotional release helped Evans fight off three break points, he still lost his serve in a lengthy game but regained a foothold in the set by taking Machac's serve in the next game.
Evans pointed to his temple in celebration, illustrating he needed a strong mentality to come through these tough moments.
More resilience was needed to fight off another break point for a 2-1 lead and Evans had the impetus as Machac lost serve for the second straight game.
The trajectory of Evans' level continued to move upwards until he served for the set at 5-3, spraying two forehands wide and hitting another into the net to gift the break back.
All that momentum which Evans had regained was quickly lost as Machac took control once again, winning the final five games to seal the biggest win by ranking of his career.
