My Concern with Postecoglu is in the 3 jobs he has had that are considered a success (Brisbane, Yokohama and Celtic), in 2 of those, his results were dreadful in his first season.
Brisbane - The team he took over finished the previous season 3rd. In Ange's first season, they finished 9th (out of 11) and lost more games than they won.
Yokohama - The team he took over finished the previous season 5th. In Ange's first season, they finished 12th (out of 18) and lost more games than they won.
The last time we lost more games than we won, was the season we had 2 points from the first 8 games.
He starts the first season like that with us and he doesn't last the season.
Edit: He also had a poor 3rd season at Yokohama (again losing more than he won) so he was literally a 1 season wonder there. Kevin Muscat has done a better job replacing Ange at Yokohoma, He also replaced Ange at Melbourne and did a better job there too.