Emma Raducanu won on her Billie Jean King Cup debut to haul Great Britain level with the Czech Republic and leave the qualifying tie delicately poised.
Raducanu, 19, was playing her first senior match on clay, adjusting well to the surface to win 7-5 7-5 against world number 50 Tereza Martincova.
The US Open champion leveled the best-of-five tie after Harriet Dart lost 6-1 6-0 to Marketa Vondrousova.
The nations play two singles matches on Saturday, plus a doubles if needed.
The winners will qualify for November’s finals, while the runners-up face a play-off tie the same week.
Britain are among the countries bidding to host the finals and could also still qualify as the host nation.
Following her stunning ascent in the past year, it is easy to forget how Raducanu is still a novice in terms of professional experience.
But she showed every bit of her talent and mentality to come through a tough battle with 27-year-old Martincova.
The teenager saved a set point at 5-4 in the opener before winning the next three games, and also fought back from a 4-1 deficit in the second.
Raducanu won six of the final seven games to clinch a vital victory for herself and her team, showing her elation with an enthusiastic celebration before she was hugged by her team-mates.
With illness and injury hampering her first full season on the main WTA tour, it was only Raducanu’s third match win in 2022.
“This one means so much to me,” said world number 12 Raducanu, who is set to play Vondrousova in the reverse singles on Saturday.
“This year I’ve won a lot of the first sets, I’ve been leading the match, but to actually close it out in two sets definitely gave me a lot of confidence and I’m very happy that I managed to.
“Playing on clay definitely took some adjusting, even now. The conditions were very windy and some bad bounces, so to adjust and adapt in the situation was very challenging but I’m very proud of how I dug in.
“In the beginning of the second set, I went a bit flat and everyone in my team was telling me the intensity had dropped. It is difficult to regain that but I’m very happy I did in the end.”
‘She didn’t let me play well’
Raducanu leads a new-look British side in Prague, with the side not able to call on either recently retired Johanna Konta or Heather Watson for the first time since 2010.
Captain Anne Keothavong recognizes it is a “changing of the guard” and says she is excited by the crop of young players she has at her disposal.
But they face a difficult task against the Czechs, who have won the team event six times since 2011, on the outdoor clay, even though they are without star trio Barbora Krejcikova, Karolina Pliskova and Petra Kvitova.
Dart, 25, broke into the world top 100 recently after reaching the fourth round at Indian Wells, but she was unable to deliver a strong start for Britain.
Vondrousova is ranked 32nd in the world and her quality on clay showed.
British number two Dart broke serve in the opening game but was unable to maintain the pressure – particularly struggling on her own serve and producing seven double faults – as she lost in just 55 minutes.
“It was a very challenging match. I just feel like I need some more time on the clay. I’m very inexperienced on the surface and she is a Grand Slam finalist on this surface,” said Dart.
“She definitely put me under pressure a lot. I didn’t feel my best but she also didn’t let me play well.”
Russell Fuller, BBC tennis correspondent in Prague
More often than not this year, the tight sets and the tight matches have gone against Emma Raducanu.
But here, on her clay court and British senior team debut and with victory almost essential in the context of the tie, she seemed to have more belief at the crucial moments.
The US Open champion only started to play points on clay on Wednesday, but as we have already discovered, the 19-year-old is a fast learner.
It will still require a stupendous effort for Britain to win this tie, and as a Roland Garros runner-up, Marketa Vondrousova is likely to provide a sterner test for Raducanu in Saturday’s opening match.