The trailblazer became the first Australian manager to win a trophy in a major European club competition as Spurs beat fellow Premier League strugglers Manchester United 1-0 in Bilbao on Wednesday night for their first silverware in 17 years.
A scrappy first-half goal from Brennan Johnson was ultimately enough to give Tottenham victory in a poor-quality match during which they had to survive a tsunami of late pressure from Ruben Amorim's otherwise feeble United.
But as a beaming Postecoglou celebrated the drought-busting victory at the San Mames Stadium, the only question that remained was whether victory, which guarantees Champions League football for Spurs next season, will save the 59-year-old from the sack.
It's said he is already doomed, regardless of the result. If so, what a glorious way for 'Big Ange' to make what matchwinner Johnson called a glorious "mike drop" exit - with Tottenham's first European trophy for 41 years.
But Postecoglou declared on the pitch: "I do (want to stay). I don't feel like I've completed the job here.
"The moment I accepted the role, I had one thing in my head, and that is to win something -- and we've done that now. I want to build on it."
Goalscorer Johnson paid tribute to Postecoglou, saying: "He's done his job. He says he wins in his second year and he has - and if there's ever a time for a mike drop, it's now."
But referring to his now-celebrated early season observation that he always wins a trophy in his second season, Postecoglou reflected: "It wasn't me boasting. It was me just making a declaration -- and I believed it.
"I know our league form's been terrible (currently 17th), nowhere near good enough and unacceptable, but us finishing third wasn't going to change his football club. The only thing that was going to change this football club is us winning something, and when I said that, that was my intent.
"If I fell short. I was happy to cop it, but I believed it inside me. That was my ambition. I wanted it stated - and I was prepared to wear it if it didn't happen."
It did happen - and his players wanted to remind everyone about Postecoglou's quote as they carried around a banner proclaiming it. There's no question they're 100 per cent behind Postecoglou and his Australian-flavoured backroom of Nick Montgomery, Sergio Raimundo and Mile Jedinak.
No matter that salvation came from a wretchedly ordinary affair to climax Europe's second-tier continental competition, one befitting two mediocre EPL sides who've lost 44 games between them this season.
Not that the Spurs' faithful will care one jot after they prevailed in this survival of the unfittest, eventually prevailing through Johnson's scruffy goal and some defensive heroics from defender Micky van de Ven and goalkeeper Guglielmo Vicario.
Rasmus Hojlund had a header cleared acrobatically off the line by van de Ven while Vicario, who'd already made a key second-half save from Alejandro Garnacho, pulled off another superb stop in the 97th minute from Luke Shaw's header.
And Postecoglou deserved praise for getting so much right in the final. Dropping the not fully fit Son Heung-min to the bench was a big call, but the South Korean was able to play a part as sub, declaring himself "the happiest man in the world".
Supposedly too gung-ho and careless in approach, and too stubborn to plump for conservatism when required, the striking thing about Tottenham's late-season European march has been his pragmatism.
"I've always felt that kind of knockout football is different from league football. It comes down to really good organisation, having a real clear game plan," he explained.
"I always felt comfortable that if we got ahead, that we could sort of negate most of what Man U were going to throw at us."
And that's what Spurs did. Johnson's goal effectively summed up the game - a messy affair three minutes before halftime as he may - or may not have - got the final touch to deflect the ball into the net from Pape Sarr's right-footed cross that ricocheted off the hapless Shaw.
From then on, Tottenham were happy to settle for what they had, because what they had meant the world.
"Ever since I came here, it was 'Tottenham are a good team but they can never get it done'," beamed Johnson.
"We got it done."
