The ninth-seeded de Minaur got the better of Germany's Jan-Lennard  Struff 7-6 (7-3) 6-4 in windy conditions on Monday, facing just one break point despite making only 48 per cent of his first serves.
He remains one win ahead this year of fellow top-10 players Jannik Sinner and Casper Ruud, who both play on Tuesday. Â Â Â
After holding his nerve, and serve, through five deuces to take a 5-3 lead in the second set, he coolly closed out the win after one hour, 49 minutes.
"It wasn't going to be easy. It's super-tough conditions," de Minaur said.
"I just tried to keep my head and keep composure. I was able to get a little bit lucky in big points today."
Demon on the rise in The Magic City 😈— ATP Tour (@atptour) @alexdeminaur sets up a fourth round clash against Marozsan, after seeing off Struff 7-6(3) 6-4.@MiamiOpen | #MiamiOpen pic.twitter.com/vKiQAjU8nNMarch 25, 2024
He will next face Marozsan, who followed up his shock defeat of world No.7 Holger Rune in the round of 64 by knocking out Australia's Alexei Popyrin in straight sets on Monday 7-5 6-3. Â
The Hungarian beat de Minaur last year at the Shanghai Masters, and the world No.10 is expecting another tough battle in Miami.Â
"He got me last time, so I know exactly what to expect," de Minaur said.
"He's a hell of a player, he's playing great and he's super-dangerous."
German fourth seed Alexander Zverev showed his quality as he escaped a tight first set en route to a 7-6 (7-4) 6-3 win over Christopher Eubanks.
"It was a difficult match. He was in control of it throughout the first set," said the former Miami finalist.Â
"I was just hanging on and sometimes that is just what you need to do."
Zverev will next face 15th seed Karen Khachanov, who converted his fifth match point for a 6-1 5-7 7-6 (7-5) win over Argentine 20th seed Francisco Cerundolo.
- with AP
