With only one player in the 23-man squad he named for two World Cup qualifiers on Tuesday based in Australia, Postecoglou is forced to spend time on the road watching matches in Britain, the Netherlands, Germany, Denmark and Austria.
It is an experience that sometimes compares highly unfavourably with Australia's A-League, he said.
"Watch some football from Europe. It's hard to watch. It's very poor in standard," the 51-year-old told a news conference on Tuesday.
"I'm not just talking about the UK. I've just come back from Europe and I won't mention the clubs but I saw a couple of first-division games and I could have walked out at half-time.
"That's not a knock on them, it's paying credit to our competition."
Postecoglou has long maintained that Australia has an unnecessary inferiority complex when it comes to football and has little time for those who think the Socceroos should count themselves lucky just to get to World Cups and the like.
The same clearly goes for the A-League, where Postecoglou spent most of a successful club coaching career before landing the Australia job in October 2013.
Aaron Mooy's early success on loan from Manchester City at English second tier club Huddersfield should have surprised no one given his outstanding form in the A-League last season, he said.
"The only surprise was he wasn't picked up by a Premier League club," he said. "I'm sure that will happen at some point. Maybe he'll get Huddersfield up and they'll sign him.
"If anything I think he's got more in him. They haven't seen his goals yet and he'll start scoring a few as well.
"We shouldn't continually seek some sort of validation for our competition," Postecoglou added.
"If a player does well in our competition it means he's got to be a good footballer."
(Reporting by Nick Mulvenney in Sydney, editing by Sudipto Ganguly)
