The coach and his new captain both tried to look on the bright side after their team surrendered a healthy lead to lose a friendly against South American opposition in London
Australia, playing in their second friendly under the new head coach, raced into a commanding 3-0 lead within the first 32 minutes of the game at The Den.
It proved to be something of a false dawn however, as the South American side asserted themselves in the second half, romping home to a dramatic victory after substitute goalkeeper Mitch Langerak received a red card.
"Obviously disappointed," Postecoglou told Fox Sports shortly after the final whistle.
"Little bit heartbreaking for the lads that we couldn't hold out for at least a draw. It was some useful lessons we'll learn out of it. We exposed some of our young players to a whole (new) level of football in a pretty hostile environment and they're massive positives for us.
"You prefer not to be in that situation. The game got a little bit out of control for us, they lifted their game. We just couldn't get hold of the ball unfortunately. We look like we got a bit tired and ran out of legs in certain areas. We made some mistakes. It's a good lesson of what you can and can't do."
The positives for Australia included a commanding debut from young centre-back Curtis Good, as well as a cameo off the bench for another debutant, Swindon Town's Massimo Luongo. Mature newcomer Alex Wilkinson will remember his first cap less fondly after he gave the ball away in the lead-up to Ecuador's late winner.
"I have absolute belief in what we can do, in what our young players can do," Postecoglou said.
"The first half was very good. We caught them by surprise, they probably underestimated us a little bit. But ultimately it's about a 90-minute performance. We paid a price and we can't let that happen again."
Asked what comes next for the Socceroos coach and his staff ahead of the friendly against South Africa on May 26, Postecoglou said: "Continue to work, monitoring our players. We'll have a good look at this game. Analyse again what we did wrong, what we didn't. Have a look at our opponents and make sure we keep taking steps forward. It may not look like we took a step forward tonight but I think we did."
Midfielder Mile Jedinak, appointed captain for the game and scorer of the second goal from the penalty spot, admitted the Socceroos struggled to cope with the team that finished fourth in CONMEBOL World Cup qualifying when they finally began to play.
"They decided to have a go, a proper go," the Crystal Palace man said.
"We got caught flatfooted a couple of times. They're a good side, they've made the World Cup. We studied them and they brought some of the guys we looked at in the video on in the second half. We knew it was going to be difficult. Having a man sent off, you're up against it."
"Everyone wants to express themselves. We all back each other. We're all in it together. One in, all in. We need to try and do what's been asked of us and I thought we implemented that really well in the first half."