Elena Rybakina has made a hot start to this summer's United Cup, destroying Jessica Bouzas Maneiro 6-2 6-3 to help Kazakhstan to a tense 2-1 victory over Spain.

Spain went ahead 1-0 in Friday's mixed-teams tie at RAC Arena in Perth when former world No.10 Pablo Carreno Busta defeated Alexander Shevchenko 6-2 6-1 in 61 minutes.

That meant Rybakina needed to win her singles match to keep the tie alive, and the world No.6 didn't disappoint.

The 2022 Wimbledon champion raced to a 4-0 lead in the first set on the way to the dominant victory in just 78 minutes.

Rybakina returned to the court for the deciding mixed doubles, teaming with Shevchenko to post a tense 7-6 (7-4) 6-7 (7-2) 10-7 victory over Carreno Busta and Yvonne Cavalle-Reimers.

The 2-1 win over Spain has thrust Kazakhstan to the top of Group C, which also boasts powerhouse Greece.

Spain will be back in action again on Saturday night when they face star Greek duo Stefanos Tsitsipas and Maria Sakkari.

"The first match back is always hard, and she's great player," Rybakina said of her singles victory over world No.54 Bouzas Maneiro.

"She had some good wins this season against top players.

"I started a little bit better than her. I played pretty aggressive."

Rybakina was the underdog 17th seed when she came from a set down to defeat Ons Jabeur 3-6 6-2 6-2 at Wimbledon two years ago - becoming the first player representing Kazakhstan to win a grand slam singles title.

But her heroics weren't rewarded with any rankings points, given there were none on offer at SW19 that year due to Russian and Belarusian players being banned.

Nevertheless, the triumph thrust Rybakina onto the world stage, and she nearly followed it up with success at the 2023 Australian Open, only to lose the final 4-6 6-3 6-3 to Aryna Sabalenka.

Rybakina reached the quarter-finals at this year's French Open and the semi-finals at Wimbledon, but she pulled out after the second round of the US Open due to a back injury.

She spent the next two months on the sidelines recovering, using the time to achieve some other personal goals.

"I got my driver's licence," Rybakina said.

"I said earlier this year that this is one goal outside of the court. So I'm pretty happy."

Rybakina is aiming big for 2025, but knows she will need to avoid any lengthy injury setbacks to achieve her goals.

"I think that's the most important for me to stay healthy, to play from beginning to the end," she said.

"I'm focusing on the grand slams and trying to get some big titles."

The night session at RAC Arena saw China's Gao overcome cramps and injury to beat Brazilian world no.17 Haddad Maia 5-7 6-4 7-5 in a battle that lasted three hours and 22 minutes, the longest WTA singles match in the history of the United Cup.

"I have no idea what's going on right now. My brain was empty and my whole body was cramping," world no.175 Gao said after beating the US Open quarter-finalist.

Zhang Zhizhen then eased past Thiago Monteiro 6-3 6-0 in the men's singles match as China built an unassailable 2-0 lead in the Group E clash, ensuring victory ahead of the mixed doubles.

Australia, led by Alex de Minaur, begin their campaign in Sydney on Saturday against Argentina.