A Richarlison penalty, won by Lucas Bergvall, was the difference between the two teams on the night.
Postecoglou later said: "For the most part I thought we did OK, could probably add a couple more goals but overall considering the context of all the changes I thought we did OK."
On his half-time change, replacing Timo Werner for Brennan Johnson, he said: "Timo was getting in good areas but he is obviously low on confidence. With Brennan on the bench I thought it was a good time to get him on and put Mikey (Moore) on the left, he's more comfortable out there.
On Moore's performance, he continued: "Yeah it's exciting. Every challenge we throw to him he thrives on. He's a great kid, working hard every day, and its exciting for us and the football club."
On James Maddison giving the penalty to Richarlison after a discussion, Postecoglou added: "As long as they score mate I couldn't care less. As long as they work that out.
"You can only face what is in front of you and that is what we have done so far. Three wins is a decent start and we will be ready for the next challenge."