The 60-year-old manager had very little time to prepare his players, having taken over the role on Tuesday following the club’s split with Nuno Espirito Santo amid a reported rift with owner Evangelos Marinakis.
In his post-match press conference, the former Spurs boss cited a “very disruptive week” as a key factor behind the team’s struggles though expressed confidence in quickly shaping the squad, saying it “won’t take long” to imprint his playing style on his new team.
Postecoglou said: "It is no secret it has been a very disruptive week for the players. Seven days ago their world was totally different from what it is today and you've got to understand that, I certainly do.
"I can't fault the players endeavour and effort. I thought we hung in there, we never really had control of the game at any point but we worked really hard in the first half and there were small seeds towards the end of the first half of us maybe being able to cause them some problems but the second goal straight after half-time killed the game.
"You can't accept defeat and you've got to be disappointed by it but in the context of what the week has been like, I can't fault the players in terms of what they were trying to do."
When asked how long it would take to shape the team in his image, he added: "It won't be months, it won't be weeks, it'll be Wednesday.
"I can't afford to waste time. This is not a project. This football club had a strong season last year, needs to be stronger this year and my job is to get us where I want us as quickly as possible.
"So by Wednesday night we will start seeing some real principles being embedded. It won't take long and I am not going to let it take long. I'll make sure we turn it around because we have got an unbelievable opportunity this year to make an impact and I'm not going to let that slip."