World No. 2 Iga Świątek clinched the decisive point by beating Eva Lys 3-6, 6-3, 6-4 in a hard-fought women’s singles clash, Polish state news agency PAP reported.
"It was tough" Świątek said after the match. "She was really going for it, especially in the first set."
"It's not easy, the first match of the season, but I'm happy we won," she added.
Earlier, teammate Hubert Hurkacz produced a surprise victory over world No. 3 Alexander Zverev, winning 6-3, 6-4 in his first competitive match since June following knee surgery.
"It’s been a while since I’ve been competing," Hurkacz said. "For seven months we didn’t know when I could get back on court. Today I was just trying to enjoy every moment."
Hurkacz, now ranked 83, underwent surgery in early July and said serving well helped him regain confidence.
"It’s a nice feeling to find a good rhythm again," he said.
The singles victories gave Poland an unassailable lead regardless of the result of the mixed doubles match between Poland’s Jan Zieliński and Katarzyna Kawa and Germany’s Zverev and Laura Siegemund.
Poland will face the Netherlands on Wednesday in Sydney as it seeks a place in the quarterfinals.
The Dutch lost 0-3 to Germany on Sunday.
Eighteen national teams are competing in Sydney and Perth, divided into six groups of three. Group winners and the best runners-up from each city advance to the quarterfinals.
The United Cup is a warm-up event for the Australian Open, which begins on January 18 in Melbourne.
(gs)
Source: IAR, PAP