The Australian No.1, a picture of despair just a couple of nights earlier after feeling he'd thrown away victory during defeat to Lorenzo Musetti, started his unlikely resurrection with a backs-to-the-wall 7-6 (7-3) 6-3 win over Taylor Fritz on Thursday, his first ever victory at the season-ending championship.
Then after achieving the two-sets-to-nil triumph - the only way he could stay in the tournament - de Minaur owed a huge vote of thanks to Carlos Alcaraz, who sealed the end-of-season world No.1 ranking by beating home favourite Musetti 6-4 6-1.
"I mean, sport," de Minaur smiled, even before the Alcaraz match. "Couple of days ago was one of the toughest days I've had in my career. I was in a very, very dark spot.
"I could tell you that I hated the sport. Now here we are two days later, and I'm feeling great about myself. It's incredible."
So, against all odds, 'Demon' finished second behind Alcaraz in the Jimmy Connors Group, qualifying for the semi-finals. He's only the third Australian ever to do so after John Newcombe (1973-74) and Lleyton Hewitt, the 2001 and 2002 winner and 2004 finalist.
That had looked totally improbable after world No.7 de Minaur had been left completely dejected, losing after serving for the match against weary home favourite Musetti on Tuesday at the Inalpi Arena.
At his post-match news conference, admitting that losing matches he felt he should have won was "getting to a point where mentally it's killing me", he added if he didn't get it sorted, "it's going to eat me alive".
Yet on Thursday, with a sympathetic crowd right behind him, the 26-year-old Sydneysider showed magnificent resolve to down big-serving world No.6 Fritz.
It didn't come easy. De Minaur was locked at 4-4 and down 0-30 on his serve in the opening set, with Fritz threatening to win the stanza which would have condemned him to an early exit.
Instead, he rebounded in that game, went on to dominate with a brilliant tiebreak and then asserted his supremacy in a largely one-sided second set to finally win an ATP Finals match at the sixth attempt, after going winless on debut last year and then losing to Alcaraz and Musetti earlier this week.
After triumphing in an hour 34 minutes, de Minaur looked to the heavens and shook his hands in joy before going over to the courtside TV camera and scrawling "Finally" alongside a smiley emoji on the lens.
"I've dealt with a fair bit of heartbreak recently. It was good to - finally - get a win," he sighed.
"More than anything, regardless of the result today, I had made peace with myself. I was okay with the result not going my way. I just wanted to play my way. It felt good to play on my terms.
"I was gonna leave everything out there today and I ended up with a really good match from the start 'til the end. It was good to get some positive reward for that hard work."
De Minaur reckoned he was "incredibly lucky to have the support system that I have", giving a special mention to fiancee, Katie Boulter, who'd cheered him on at courtside.
When told by his interviewer that he would make the last four if Alcaraz beat Musetti, he said: "Is that actually true or not? I don't know. I don't trust you right now.
"Whatever happens, happens, but I won't be paying too much attention to the tennis. I'll be relaxing and having a nice night here in Torino."
And how nice it turned out to be as Alcaraz, looking ominously good, completed his third consummate victory of the week in just 83 minutes to become a two-time year-ending world No.1.
"I had to handle my nerves the best I could and I was happy the way I did it," said the Spaniard, who's had an incredible year with eight titles and two grand slam titles in Paris and New York.
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