Elena Rybakina marked her United Cup debut by helping Kazakhstan to a 2-1 victory over Spain at the season-opening tournament in Perth, Australia.
The 25-year-old, who was Wimbledon champion in 2022, beat Jessica Bouzas Maneiro 6-2 6-3 to level the match after Pablo Carreno Busta defeated Alexander Shevchenko 6-2 6-1 to give Spain the lead.
Rybakina, the world number six, then partnered Shevchenko to a 7-6 (7-4) 6-7 (2-7) 10-7 win against Carreno Busta and Yvonne Cavalle-Reimers in the mixed doubles.
Great Britain will get their campaign under way against Argentina on Monday, before facing Australia on Wednesday.
Kazakhstan will qualify for the quarter-finals of the 18-nation mixed teams event if they defeat Greece in their second Group C match on Monday.
Rybakina, playing for the first time since beginning work with fellow former Wimbledon winner Goran Ivanisevic as her new coach, said: "The first match is always difficult.
"It's not easy to get used [to it] that quick but I'm pretty happy with the way I played today."
The third edition of the United Cup runs until 5 January 2025, with matches taking place in Perth and Sydney.
GB's group fixture against Australia will see British women's number one Katie Boulter face fiance Alex de Minaur. The couple announced their engagement earlier this week.
The Australian Open, the first Grand Slam of the season, begins on Sunday, 12 January.