"Nothing's changed. I've said it now. I don't say things unless I believe them."
It's a statement that can quite easily fall flat on its face, especially as the manager of a club without a trophy in 17 years.
Fast forward to May and Postecoglou is in a position to back up his words, guiding Spurs into the Europa League final after winning their semi-final second leg 2-0 at Bodo/Glimt.
Getting to this stage has – quite obviously – come with its challenges for a Spurs side down in 16th in the Premier League and earlier dumped out of both the FA Cup and League Cup in the space of a week.
The Europa League hasn't been plain sailing for them either, despite finishing the league phase in a decent fourth place.
Spurs teetered on the brink of a last-16 exit after a 1-0 first-leg defeat at AZ Alkmaar and faced a daunting trip to Eintracht Frankfurt in the quarters while only mustering an opening home draw.
And even though things were on the up for their semi-final second leg after a 3-1 triumph at home, there was a job still to be done.
But Tottenham made it happen and it was down to some micro tweaks made by Postecoglou as his team did battle in unfamiliar surroundings.
Playing the occasion
All the talk was about Bodo/Glimt's artificial playing surface, the conditions while playing inside the Arctic Circle and the hosts losing just once at home all season in the Europa League.
Also having to do it without injured midfielders James Maddison and Lucas Bergvall – two of Spurs' best performers over the last couple of months and players who can be trusted with the ball.
Essentially, it was a recipe for disaster on paper for Spurs, who have in the past come apart at the seams at the first sign of pressure or adversity.
But none of that froze Spurs or Postecoglou, who showed he can be adaptable in his ways.
Knowing a two-goal lead in the tie could change very quickly, Spurs did away with playing out from the back, which is what Postecoglou has rigorously drilled into his players.
The artificial pitch was drenched beforehand despite it receiving plenty of rain throughout the day – something that could have tripped Spurs up like it has with other sides.
Guglielmo Vicario abandoned looking for one of his defenders and instead went direct, knowing forwards Dominic Solanke and Richarlison could outmatch their opponents physically.
It didn't always come off, but Spurs looked more than content to go long to get up the pitch, lowering the odds of errors at the back.
Dark arts?
But there were other elements from Tottenham that showed they were there to grind out a result and not muck around, including slowing the game down.
Under Postecoglou, Spurs have been typified by getting play restarted as fast as possible and it has often led them to play into trouble.
There was absolutely none of that on Thursday in Norway.
Vicario mulled as long as he possibly could over goal-kicks, testing referee Maurizio Mariani's patience before eventually being booked during the second half.
Spurs also made it a bitty, rubbish game when the ball was in play that it hindered any momentum a chasing Glimt side tried to feed off.
Plenty of throw-ins and corners made it such a disjointed affair that you could sense the frustration building from the hosts and supporting crowd.
For Tottenham and Postecoglou, though, the plan worked perfectly.
"Perfect" has been anything but for Postecoglou's Spurs, yet here they are, in the position to win their first European trophy in 41 years.
With a similarly bizarre Manchester United side awaiting, there should be an element of confidence from a Tottenham perspective given they have beaten them three times already this season.
The truth is, potentially hoisting the trophy on May 21st might not be enough for him to save his job, but he has given himself and his players a huge chance to eat their words.
It would be the perfect mic-drop after all.