Postecoglou played Archie Gray, Mikey Moore, Will Lankshear and Lucas Bergvall for their Europa League win at Ferencvaros last night.
He said afterwards: "How many 17-year-olds are playing in the Premier League? Yeah, Yamal is brilliant but it's not a common thing. It's still pretty rare because you have to take into account, not just their physical maturity at 17 of being able to handle it, their emotional maturity, you've got to be really careful.
"There are always exceptions to the rule and Yamal is certainly one of them, but like I said, if you look at the Premier League, how many 17-year-olds are actually contributing and Mikey is already to is, which shows that he's got something special, but we've just got to be really careful about how we develop that.
"I think because it's too easy just to say, oh, you know, he's a great young player just throw him in there, especially in the Premier League because of all the leagues probably in Europe, it's the most physically challenging. So young players, the first thing I want to see is can they handle it and to be fair, Mike handles it pretty well, and certainly Archie and Lucas have that, but we've got to be careful with them.
"But at the same time, we've brought some really talented young players to the club and part of my pitch to them was that we will develop them and they will play and it's my responsibility to make sure they do that. I can't shy away from that because the next 18 or 17-year-old who I sign will point to recent experience. So it's important we give them the game time they deserve."