Swiatek needed just 52 minutes to extend her singles winning streak to 19 in her second competitive match since becoming world No. 1.
“It took us a few years, step by step, to progress and qualify finally,” the 20-year-old Swiatek said in an on-court interview. “Hopefully in the finals we’re going to show even more progress. I’m really proud of us.”
Swiatek’s victory made it 3-0 for Poland in the best-of-five qualifier for the finals in November. The 2020 French Open champion beat Mihaela Buzarnescu 6-1, 6-0 on Friday.
Italy and Kazakhstan also advanced on Saturday. Camila Giorgi beat Harmony Tan of France 6-2, 6-0, giving the Italians their third straight win. Elena Rybakina made it three in a row for Kazakhstan over Germany by beating Angelique Kerber 4-6, 6-3, 7-5.
Raducanu, slowed by a blister on her foot, had debuted in the competition with a victory over Tereza Martincova on Friday but struggled against Vondrousova on a cold morning at the outdoor clay court.
Vondrousova, a former French Open finalist playing on her home court, needed just 62 minutes to beat the 19-year-old Raducanu, who took a medical timeout after the first set.
The Czechs 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.