Australia's tilt at the inaugural United Cup is effectively over after just one tie, with Great Britain winning through to the Sydney play-off by completing an upset win over Spain.
The British team will face the United States in the first knock-out stage, beginning on Wednesday.
In the box seat for victory over the Spaniards after establishing a 2-0 lead in the Group D tie, Great Britain went on with the job in Sydney on Sunday night.
Dan Evans was the hero for the Brits after sealing an unassailable 3-1 advantage with a grinding win over Albert Ramos-Vinolas.
It came after Great Britain had beaten Australia 3-2 in its opening tie.
With only the top team in each of the six groups progressing to the next round, Spain joins Australia on the sidelines after the first phase.
Their players will, however, get some more match practice over the next two days when Australia and Spain meet in a dead tie.
Australia had high hopes coming into the tournament with a squad featuring Nick Kyrgios, Alex de Minaur and Ajla Tomljanović
But Kyrgios's 11th-hour withdrawal, and injury to two-time Wimbledon quarterfinalist Tomljanović, put Australia's campaign into disarray.
Despite their advantage, the British still had some work to do on Sunday when Harriet Dart went down to Paula Badosa 7-6 (8/6), 6-7 (7/5), 1-6.
Dart belied her world ranking of number 98 to push Badosa all the way, at one stage only two points from winning the match in a thrilling second set tiebreaker.
But the number 13 steeled herself when it mattered most and ran away with the third set to get Spain back in the tie.
With Nadal waiting in the wings for a potential deciding fifth rubber, much hinged on what Ramos-Vinolas, a replacement for Pablo Carreno Busta, could do against Evans.
After a sluggish first set, the Spaniard roared back to life in the second and Evans, a disappointing first-up loser to Australia's Jason Kubler, looked on edge entering the decider.
However, the world number 27 secured a vital break in the seventh game and ultimately served out the contest for a 6-3, 1-6, 6-3 win, rendering the mixed doubles a dead rubber.
"I don't feel my strongest but I've got a great team behind me," Evans said.
"It helps that it's not a regular tournament; it's tough to throw the towel in when you've got all that lot behind you."
US go through
The US secured its passage through to the Sydney play-off round against Great Britain after taking a 2-0 lead in its Group C tie against Germany.
Taylor Fritz got his team off to an excellent start, beating an underdone Alexander Zverev in straight sets.
Zverev with fitness and timing, winning just 57 per cent of points on his serve.
The world number nine Fritz was switched on, however, racing through the first set 6-1, before being pushed slightly harder in the second.
He clinched the match 6-1, 6-4 in 64 minutes.
Fritz's compatriot Madison Keys then beat Jule Niemeier 6-2, 6-3, with the US only needing to win two rubbers to progress through to the knock-out stage.
The US-Germany tie concludes on Tuesday.