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The Brazilian, who is just 18, has reached this stage at an ATP 1000 Masters tournament for the first time having defeated No.19 seed Ugo Humbert in a clinical display, winning 6-4 6-3.

De Minaur was relatively untroubled himself on route to the third round and dealt well with China's big-serving Bu, claiming two of the five break points he manufactured, both crucially at 4-5 in both sets.

The No.10 seed served superbly himself, losing only four points on his first serve and never once coughing up a break point.

De Minaur, who joins fellow Aussies Jordan Thompson and Adam Walton in the next round, now boasts a 15-1 record against players outside the top 30 this season and will hope that stands him in good stead against Fonseca in the next round to extend his bid to improve upon his fourth-round Miami run last year.

But while Fonseca is ranked just inside the top 60, he is as dangerous as they come and is rising up the charts rapidly.

After his win today, he is the youngest player to make the an ATP 1000 Masters third round since Carlos Alcaraz did so in Paris in 2021.

Alcaraz, though, was eliminated by David Goffin in a second-round upset, and Fonseca will be looking to do the same to De Minaur when they meet for a spot in the last 16.

The pair has yet to meet on the professional circuit, and De Minaur will need to be wary not just of Fonseca's power but also his popularity.

“When the crowd is with any player, they are more hyped,” Fonseca said after receiving huge support during his match and eventual victory over Humbert.

“I started the match today super relaxed, with no nerves. That was good, I served well. I had a quick break, he was maybe a little bit more nervous in the beginning, but I started well and that’s what made the difference.

“Against lefties, they like the crosscourts with their forehand. My backhand today was pretty good and I had the chance to play more aggressively with my forehand. I didn’t let him have opportunities on my serve [either].”