The Australian coach's opening game in charge since being sacked at Tottenham in June ended in a resounding 3-0 defeat to their arch north-London rivals Arsenal on Saturday.
Naturally he was taunted mercilessly by the home crowd for his Spurs connections as he watched his new Forest charges succumb from the sidelines.
"Are you Tottenham in disguise" they chanted as the goals rolled in for the Gunners.But the 60-year-old, while admitting the result was a "disappointing" start to life at Forest, insists there is no time to waste as he looks to get them firing, starting against Swansea in the Carabao Cup on Wednesday .
Could it take months? he was asked in his press conference after the defeat the Emirates Stadium. His response was classic Ange:
"Oh no, mate. It won't be months, it won't be weeks. It will be Wednesday.
"I cannot afford to waste time. This is not a project. This football club had a strong season last year, they need to be stronger this year, and my job is to get us to where I want us as quickly as possible.
"On Wednesday night, we will start seeing principles being embedded. It won't take long and I will not let it take long.
"I will make sure we turn it around because we have an unbelievable opportunity to make an impact this season, and I am not going to let that slip.
"We've got two sessions before that. We've got another couple of sessions before the next Premier League game, so whatever's happened this week, and how disruptive it's been, we can put a line through it and start looking ahead."
He was brought in to replaced Nuno Espirito Santo last Tuesday after the Portuguese coach was sacked having clashed with Forest owner Evangelos Marinakis.
And with precious little time to galvanise his new team, former Socceroos boss Postecoglou admits preparation for the Arsenal clash was far from ideal.
"Seven days ago, their world was totally different to what it was today. You've got to understand that. Some players were away on international duty. The other players had the whole weekend off. They only got back in on Tuesday," he said.
"So, you know what they left, when they left the club, to what they inherited, was totally different, with new faces, new voices, new coaching and new training. We've only had one training session together."
The man who steered Tottenham to Europa League success last season, ending their 17-year wait for silverware, is determined for more of the same at Forest.
"They're all big jobs. I haven't taken over an easy one yet but that's why I'm here. I love the challenge and we'll get to where we want to," he told TNT Sports.
"It hasn't been an ideal prep for the players and you have to take that into account. All you can ask for is effort and unfortunately, against a very good opponent, today was a bridge too far.
"This is a group of players who showed last year how hard they fight for each other. Disappointment today but there's only one way to respond."
