There's no such thing as a meaningless match for Alex de Minaur.

The Australian registered his first-ever win over 22-time grand slam champion Rafael Nadal at the United Cup, downing the Spaniard 3-6, 6-1, 7-5.

While not on the biggest stage — the clash was part of a dead tie, with Great Britain already progressing to the next round of the competition — it's still one of the best of the 23-year-old's career.

Until Monday night in Sydney, de Minaur had never beaten a player ranked No.1 or No.2 in the world.

Now he has beaten arguably the best of all time.

"I knew it was going to be a battle — Rafa is a hell of a competitor."

World No.2 Nadal started inauspiciously, going down an early break, only to reel off four straight games to snatch the first set.

That momentum continued with another break to start the second set, only for the Sydney local to produce some of his own trademark grit and storm through the next six games.

The decider was a mixed bag — de Minaur's foot speed and ability to rip out winners from defensive positions against the brute force and experience of Nadal.