The Australian survived a hail of winners from powerhouse Jan-Lennard Struff but emerged the stronger after a four-and-a-half hour stoppage to win 4-6 6-4 6-3 6-3 on Saturday, becoming the first Australian man for 17 years to reach the singles last-16 since his Davis Cup captain Lleyton Hewitt.
And at the end of a match that took over eight hours to complete, de Minaur reckoned he had discovered "gold at the end of the tunnel".
"Another huge mental battle," sighed the 25-year-old.
Alex De Minaur reckons he third-round triumph was one of his best. (AP PHOTO)
"It was probably one of my best performances, mentally, in my career to turn that match around with the conditions, with everything really against me."
On another grey, dank Paris morning, the 'Demon' had a devil of a job coping with a rejuvenated 34-year-old giant playing lights-out tennis as he lost the first set and was reeling at 1-3 down in the second.
"Everything couldn't get any worse, right? I knew that this was just his (Struff's) ideal conditions to a T. Slow, heavy, rainy, muddy, he's able to hit through the court and not make a lot of mistakes.
"I just told myself the only chance or way I was going to win was just to fight 'til the end, fight every single point, keep battling, try to stay in no matter what. That's what got me the win.
"Sometimes you don't get rewarded, but a day like today where I'm backed against the wall, a lot of things going against me, and managing to kind of find the gold at the end of the tunnel, it's huge.
"It kind of gives me that confidence that I can do it again and again now.'
Indeed, de Minaur can consider the day he defused Struff's thunderous game in six minutes under three hours in front of a largely pro-German crowd to make the second week in his least productive grand slam to be another key moment in his blossoming career.
He fought back to take the second set but was 2-0 down in the third when the rains came for the fifth straight day at this trying Roland Garros.
It's played on de Minaur's nerves all week, the Aussie No.1 complaining that the constant interruptions to matches in the cold, damp conditions had added years to his life.
But it was the booming groundstrokes of world No.41 Struff that had looked more designed to give him grey hairs, as he had crashed 32 winners past the 11th seed before the stoppage came.
But it proved a timely one for de Minaur, as Struff admitted.
De Minaur was on the receiving end of a barrage from Struff before prevailing. (AP PHOTO)
"After the rain, I felt he came on very well, played a bit more aggressive. At the end, he was playing very good, hitting very deep balls, getting into offensive positions," said the German. "He did a great job."
Indeed, when play finally resumed at 5.30, Struff's guns were spiked.
De Minaur, at 3-1 down in the third, reeled off five games, and a break in the third game of the fourth was crucial, though de Minaur did suffer some nervous moments as Struff had two break points to get back on serve at 4-4.
But de Minaur wouldn't be denied, and, afterwards rushed over to hug a kid at courtside who had been a non-stop cheerleader on this longest day.
Then he could ponder the prospect of a fourth-round date with old foe, fifth seed Daniil Medvedev, who overcame Czech Tomas Machac 7-6 (7-4) 7-5 1-6 6-4.
De Minaur was the first of the two remaining Australian singles players in action, with Thanasi Kokkinakis, creaking into the fray again after two exhausting five-setters, having his match with 12th seed Taylor Fritz, the American No.1, rearranged to take place on the same Court 14 immediately afterwards.
