Alex de Minaur swept past Tomas Martin Etcheverry to win his first match of the season Saturday but it was not enough to prevent Argentina from upsetting hosts Australia at the United Cup, while Switzerland beat France.
The world No 9 crushed his opponent 6-1, 6-4 to level the tie after teammate Olivia Gadecki crashed against Nadia Podoroska 6-2, 6-4 in the women's singles rubber at Ken Rosewall Arena in Sydney.
But the home side couldn't lift in the deciding mixed doubles with Etcheverry returning to partner Maria Carle and beating Matt Ebden and Ellen Perez 6-2, 6-4.
Despite losing the tie, De Minaur was happy with his early-season form.
"I've been putting in some great work in the pre-season," he said.
"I felt comfortable with the way I was playing before the tournament, so I just told myself to back myself and play the type of tennis I wanted to play."
Former Olympic gold medallist Belinda Bencic won her first tour-level match since the 2023 US Open to help Switzerland beat France.
The 27-year-old, a one-time world No 4 who is now ranked 487, took down Chloe Paquet 6-3, 6-1, winning 10 of the last 11 games.
While she tentatively returned to the court at low-key events in November after having a baby in April, it was her first win at tour level since her third-round victory at the 2023 US Open.
Her teammate Dominic Stricker slumped 6-3, 7-5 to Ugo Humbert in their singles clash to send the tie to the mixed doubles.
Bencic fronted up again alongside Stricker to down Edouard Roger-Vasselin and Elixane Lechemia 6-1, 7-6 (7/4) and earn Switzerland the win.
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"I'm really excited to be back, of course," said Bencic, who won Olympic gold at the 2021 Tokyo Games and has eight career WTA titles to her name.
"I had a little bit of nerves at the start and a little bit of rust, so I'm happy I kind of accepted that and tried to fight through it.
"And after, I felt like it went smoother, I became a little bit more calm, and kind of was more able to focus on my tennis."
In Perth, Canada bounced back after Felix Auger-Aliassime lost his singles rubber to prevail 2-1 over Croatia.
The Canadian win over Croatia came thanks to a 6-3, 6-4 mixed doubles victory from Auger-Aliassime and Leylah Fernandez against Lucija Ciric Bagaric and Ivan Dodig.
"It was all about trusting each other and not trying to go for too much," Auger-Aliassime said. "We stuck to the game plan and it worked out well."
After 2021 US Open finalist Fernandez easily dispatched Donna Vekic 6-4, 6-3 to start the tie, Auger-Aliassime got into trouble against Borna Coric, crashing 0-6, 6-4, 6-4.
Former top-10 players Maria Sakkari and Stefanos Tsitsipas relied on a mixed doubles win to complete the 2-1 Greek win over Spain, which knocked the Iberians out of the competition after they lost to Kazakhstan on Friday.
Sakkari, who once stood third in the WTA ranking, showed signs of rustiness after playing her first official match since quitting injured in the US Open first round.
She was beaten 6-2, 6-1 in singles by Jessica Bouzas Maneiro, who produced the statement win of her career a day after losing to former Wimbledon champion Elena Rybakina.
The 11th-ranked Tsitsipas levelled the evening one match apiece with a defeat of Pablo Carreno Busta 6-4, 4-6, 6-3, coming from a break down in the final set.
The deciding mixed doubles rubber was tight, with the Greek pair taking victory over Yvonne Cavalle-Reimers and Sergio Martos Gornes 4-6, 6-3, 10-6 as Sakkari set up victory with three match points.
"There's no Greek night without some drama," Tsitsipas said. "I'm glad to have her as my partner in crime, I like to have a fighter alongside me.
"She delivered at the very end."
Sakkari added: "We came through when we had to, the tiebreak set was very good from our side. There were some quite good moments."
The 18-nation mixed-team United Cup is being played in Perth and Sydney.
Each team features three men and three women, with ties comprising one men's and one women's singles and an often decisive mixed-doubles clash.
The tournament began on Friday with Spain crashing 2-1 to Kazakhstan, while China swept past Brazil 3-0.