After defeat at Emirates Stadium, Postecoglou promised this would be the game where the first signs of his influence on the team he inherited from Nuno Espirito Santo would be visible.
He did not have time to waste, he said.
And at the very least, the Australian will have gained a greater idea of what he has at his disposal after handing first starts to talent that cost the club the best part of £120m over the summer.
He would have had every right to have been impressed with Jesus, the striker nicknamed the 'Little Frog', who jumped at the opportunity to open his account in the south Wales rain.
More importantly for Forest, Jesus' second was an example of the kind of football associated with Postecoglou's teams as a sweeping move cut the hosts open and made it easy for the striker to finish.
There were signs too of Juventus loanee Douglas Luiz's class and what the likes of Hutchinson and McAtee could provide.
But there were also signs – as if the result did not make it obvious - that the former Spurs boss has plenty of work to do.
It was Swansea who looked to have the kind of tempo 'Angeball' is meant to have, pressing hard from the front with intensity.
And although Forest could point to spurned chances from a number of players, it would be tough to say that Swansea did not earn the win.
Ethan Galbraith and Mallick Yalcouye impressed and showed why there is renewed hope of the Swans pushing for a return to the Premier League.
Given this was the first time they have beaten top-flight opposition in 10 cup ties since dropping into the Championship in 2018, this result will only increase such hopes.
Image source, Huw Evans Picture Agency
