On paper, Al Nassr look clear favourites. The gap in pedigree is obvious, and Diriyah are still adjusting to top-flight life after earning promotion last season. The report says their first league outing ended in defeat to Al Ahli, which makes this an even sharper examination of their defensive organisation.
For Postecoglou, that raises the real question. Not simply whether Al Nassr go through, but whether they do it with control. His teams are usually judged on intensity and bravery in possession. Against a lower-ranked opponent, any drift, loose spacing or lack of incision will stand out quickly.
The update says Diriyah are set to start with Nikola Vasilj; Al-Faraj, Djimsiti, Mbemba, Al-Obaid; Gueye, Al-Malki; Diandy, Rodríguez, N'Koudou; Laborde.
It also says Al Nassr are expected to go with Bento; Boushal, Simakan, Martínez, Al-Najdi; Al-Khaibari, Samu Costa; Angelo, João Félix, Mané; Al-Hamdan.
That shape points to plenty of attacking thrust from Al Nassr, with creative quality behind the striker and enough pace out wide to stretch the game early.
If Al Nassr come through smoothly, attention will shift to how quickly Postecoglou settles on a core side for the bigger tests ahead. If the performance is flat, the scrutiny will start immediately.