Spurs won 1-0 with teens Mikey Moore, Lucas Bergvall and Archie Gray all in the starting line-up.
Postecoglou later said: "We had to do a little bit of everything. It’s not easy, making nine changes to the team, it disrupts the flow and rhythm of our football, but the boys handled it well for the most part. We created good opportunities, we lacked composure in the final third and had to defend on the counter attack, Fraser pulled off some good saves, which is a positive for us.
"We had three teenagers in the starting line-up, guys who have not played a lot. We will need the squad, we have a heavy programme, and to get a third win is a positive win.
"It’s great to see that. It is not just me giving them games. They are making impact, they are playing well, they are developing, growing confidence and belief, which is great. When you are talking about two 18-year-olds and a 17-year-old, it’s great for us. If they keep contributing and developing at the same time, not just for the short term but the longer term, it’s a really encouraging sign."