Irvine parallels the uncertainly of Postecoglou's continuing tenure to the situation he faced at former club Burton Albion last season, when coach Nigel Clough was seemingly set to depart for Nottingham Forest.
The Brewers, who had lost seven of their last eight games in the Championship, were in London amid heated speculation that Clough had been poached by the club he had played for.
Burton's reaction was to go out and win 2-1 at Loftus Road, with Irvine declaring that similarly nothing will derail the determination of his Socceroos brethren to prevail over two legs this month against the Central Americans.
"Last January at Burton we were basically told the day of the game against QPR that the boss had got another job and it was done and dusted that he'd go to Forest," said Irvine, who moved to fellow Championship side Hull City during the transfer window.
"People asked afterwards whether our performance had anything to do with the situation regarding the manager. Whether it had given us extra motivation.
"But it had nothing to do with that. Once you're out on the pitch all these things are far away from your mind.
"As long as you don't let it affect you off the pitch these things don't usually have much of an impact on the pitch.
"The last four Socceroos camps there's been pressure, and this won't be any different."
Irvine, who has made five appearances since heading to Humberside, acknowledges that Australia have picked the hardest possible way to reach Russia 2018, but feels the belief within the squad will get them over the line in the looming battles on November 11 in San Pedro Sula and Sydney four days later.
"We're aware of how good they will be ... qualifying for World Cups is getting harder for everybody, as you saw with Chile and the Netherlands missing out completely.
"There's been criticism of a lot of things over the last 12 months and we're just about getting on with the job."
Irvine knows that nailing an automatic starting spot with Hull is more problematic than at Burton, for whom he excelled last season with 10 league goals.
"There are several other international midfielders here and it's down to me to push myself and take my game to another level," he explained.
"I can feel myself improving on a daily basis at a club which is looking to get back to the Premier League, as soon as possible."
That, though, looks long odds at this stage with the relegated club sitting 17th in the Championship, with just 16 points from 14 games.
"I don't think the results have necessarily reflected our performances," he said.
"We're still in the part of the season where things are really tight and a run of results will see you fly up the table.
"The whole squad pretty much started from scratch this season, they lost the entire core of the team from the Premier League.
"So there are a lot of new players trying to gel in a short space of time, and a new manager (Leonid Slutsky) as well.
"It was always going to be a transition period."
