Raducanu's swift rise was evident before she beat Tereza Martincova 7-5 7-5 in what was her first match for Britain and her first professional match on clay in Friday.
Her third win of the year came with added pressure after teammate Harriet Dart lost to former French Open finalist Marketa Vondrousova 6-1, 6-0 in the opening singles. Vondrousova and Raducanu will meet in the first reverse singles on Saturday.
The Czechs are favoured to win the best-of-five qualifier for the finals in November. They have won the Cup six times since 2011 though they are without their three highest ranked singles players - No. 2 Barbora Krejcikova, No.7 Karolina Pliskova, No.28 Petra Kvitova -- and No.1-ranked doubles player Katerina Siniakova.
Elsewhere, Italy led France 2-0, Kazakhstan led Germany 2-0, Poland led Romania 2-0, and Spain led the Netherlands 2-0.
Belgium received a walkover win over Belarus after the latter and titleholder Russia were suspended for Russia's invasion of Ukraine.
Australia replaced Russia in the finals, to join 2021 finalist Switzerland and Slovakia.
Iga Swiatek celebrated her first competitive match since becoming world No.1 by thrashing Romania's Mihaela Buzarnescu in less than an hour. Swiatek extended her singles winning streak to 18 after Polish teammate Magda Linette won the first point from Irina-Camelia Begu.
Swiatek can secure Poland's place in the finals when she faces Begu in the first reverse singles on Saturday.
In Alghero, Italy's Jasmine Paolini came from a set and a break down and saved two match points to beat France's Alize Cornet 2-6, 6-1, 7-6 (2) in two-plus hours. Camila Giorgi beat Oceane Dodin 6-1, 6-2, also for the first time.
France has won from 0-2 down only once, but it was against Italy in 2015.
In Nur-Sultan, Yulia Putintseva upset Angelique Kerber 3-6, 6-3, 6-2 for a record 15th win in the Cup for Kazakhstan. Then Elena Rybakina overran Laura Siegemund to put the favoured Germans in a deep hole.
In s-Hertogenbosch, there were straight-sets wins for Spain's Sara Sorribes Tormo and Nuria Parrizas-Diaz, who notched her first Cup singles win.
In Asheville, Alison Riske and Jessica Pegula won in straight sets for the United States against Ukraine, though Riske's defeat of Dayana Yastremska included a first set that lasted nearly 90 minutes.
Riske won 7-6 (18-16) 7-5, the 34-point tiebreaker second in Billie Jean Cup history only to a 21-19 in a 2004 doubles match between India and Uzbekistan.
27°C