Alex de Minaur has pulled off one of the biggest wins of his career, defeating World No.2 Rafael Nadal on Monday night (AEDT) in Sydney.

The 23-year-old has taken a leading role during the early stages of the United Cup due to the absence of Nick Kyrgios, but will be unable to help Australia out of the early stages after Great Britain sealed to spot in Group D.

De Minaur fell behind early against Nadal, dropping the first set and a break in the second, before rebounding to secure a 3-6 6-1 7-5 victory and put the Aussies in the lead against Spain.

Speaking after the match, de Minaur admitted it was one of the landmark moments of his career to date.

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“I think it’s definitely up there,” he said.

“It’s one of those achievements that you have unlocked in your career…but also, it’s a big win for myself, one that I really needed.

“I’m gonna cherish and use, take all the confidence from this and be able to hopefully take it to have a good Aussie summer.

“It’s always a surreal experience playing here. Just walking out there and hearing the support I get on that court is pretty special.

“No secret, it is my favourite court to play on in front of friends and family. I’ve had so many great memories, and I’ve been able to add another one to it. I’m extremely stoked.”

In the second match between Australia and Spain, Nuria Parrizas Diaz stepped up and delivered a victory against Maddison Inglis.

The tie will finish on Tuesday as with Spanish star Paula Badosa takes on Zoe Hives and Pablo Carreno Busta scheduled to face Jason Kubler.