On Monday, Poland secured a 2-1 victory over Spain, earning a spot in the quarter-finals of the United Cup. Meanwhile, defending champions, the United States, faced defeat against hosts Australia, who also clinched a 2-1 victory, securing their place in the last eight. World number one Iga Swiatek displayed dominance in her singles match, defeating Sara Sorribes Tormo 6-2, 6-1. Swiatek, along with Hubert Hurkacz, sealed the win with a 6-0, 6-0 thrashing in the mixed doubles.
Although Hurkacz suffered a loss in the opening singles, falling to Alejandro Davidovich Fokina 3-6, 6-3, 6-4, the top-seeded Polish team finished Group A with a perfect 2-0 record and awaits their quarter-final opponent. Swiatek, having lost only seven games in two singles matches, expressed the mixed doubles experience as valuable practice, emphasizing the use of different skills in the format.
Australia faced a tough challenge against the United States but emerged victorious. Alex de Minaur started the momentum for the hosts by defeating Taylor Fritz 6-4, 6-2. Ajla Tomljanovic couldn't overcome world number five Jessica Pegula, but Australia sealed the win in mixed doubles with Storm Hunter and Matt Ebden defeating Pegula and Rajeev Ram 6-3, 6-1.
In Sydney, France secured a 2-1 win over Germany, with Alexander Zverev providing the opening lead by overcoming Adrian Mannarino 4-6, 6-4, 6-3. Despite Angelique Kerber winning the first set against Caroline Garcia, France leveled the tie, leading to a mixed doubles decider. Kerber teamed up with Zverev, but France ultimately won the mixed doubles rubber 7-6 (7/4), 2-6, 12-10.
In another match in Sydney, Casper Ruud led Norway to victory, winning both his singles and mixed doubles matches against Croatia. Ruud defeated Borna Coric 6-4, 6-1 and, along with Ulrikke Eikeri, secured the mixed doubles victory against Donna Vekic and Ivan Dodig with a score of 6-2, 3-6, 10-7. The win was crucial for Norway, which had suffered a loss to the Netherlands over the weekend. Ruud expressed motivation and readiness for the new year after his successful start in the tournament.