The 61-year-old Australian had a dream start to his appointment as Al Nassr coach in the Saudi Pro League when he immediately won the manager of the month award for August for four straight wins.
But with huge expectations for him to successfully defend the title at one of Saudi's 'big four' clubs as he attempts to rebuild his career after his sackings in England at Tottenham and Nottingham Forest, things have quickly turned more complicated.
The Riyadh-based champions had lost one and drawn another of their previous three fixtures while slipping to third place in the league and were looking for an impressive start to their opening match in the Asian Champions League Elite, a tournament Al Nassr have never won but have long coveted.
Instead, his side were outplayed 4-0 by the UAE champions Al Ain on Tuesday (Wednesday AEST), leaving the Australian to face a grilling from reporters afterwards. Being Postecoglou, he didn't back down from returning fire on his interrogators, especially when it came to defending his star player.
When one journalist said in the post-match press conference Ronaldo had done "nothing" in Al Nassr's last three matches, Postecoglou jumped to the defence of the 41-year-old, who returned late to pre-season following the World Cup and his wedding.
"Cristiano has scored three goals already. He had a limited preparation," Postecoglou said.
"This is not about the players. The players are giving everything, and they're top players and they've got great character.
"The responsibility is mine, but you shouldn't say that about somebody who is still setting an example for everyone.
"You should be careful when you say things like that about people who have built a career on making all the sacrifices to keep playing.
"You can criticise, you can criticise me, no problem. That's okay. Did he not score in three games? Did he not have chances today?"
When the reporter persisted that Ronaldo had done nothing, Postecoglou retorted: "He did nothing? Well, you're watching a different game to me."
Postecoglou preferred to pinpoint Al Nassr's demanding schedule, with nine matches in a month, as he looked forward to almost a month-long break amid the international window.
But how Postecoglou handles the potentially thorny problem about when to play and when to rest his previously undroppable forty-something totem as Ronaldo homes in on the amazing 1000 career goals landmark could prove the most difficult and delicate balancing act of his reign.
He has a two-year contract but there may well be no second year if Al Nassr don't successfully defend their crown.
But Postecoglou has already shown he's not afraid to substitute the megastar when necessary. Last month, he brought Ronaldo off at halftime when his 10-man side were 2-0 down to Al-Ettifaq and, without him, they fought back to win 3-2.
