The current rule of thumb is supposed to be that all wings should automatically be able to slot into the full-back role, and vice versa, but not all wing-cum-full-backs have a kicking game to match Ireland's number 15.
If his pace and flypaper hands under the high ball mean that he has several strings to his bow, that siege-gun left boot is certainly bringing him places. Not that Michael Cheika appeared to be too keen early in the season despite the fact that Kearney had been so impressive in the Lions test series, however, with such a high premium on field position these days, it was only a matter of time before last season's order was restored.
If the conditions allow today, expect Kearney to pin Australia back towards their own 22 as often as he can, and watch too for the strong running that brought him tries in the second test against the Springboks and in Leinster's recent Heineken Cup game in Brive.
Meanwhile, Australia's Mr Versatility has been in outstanding form of late, appearing in all of the Wallabies tests this season at wing, centre and now full-back. Ashley-Cooper poses a significant threat as he demonstrated at Twickenham when he powered through some admittedly feeble England defence for his 12th test try, but critically, his kicking game is nowhere near as polished as Kearney's. And that is the difference. For all Ashley-Cooper's prowess as a finisher, Kearney's boot is likely to have a far greater impact on the game.
Those who remain adamant that games are won up front may have to think again because while there doesn't appear to be a massive difference between the sets of forwards, there is something of a chasm in terms of form between the out-halves.
Reputedly the highest paid player in Australia, Giteau is the tourists' hub, their playmaker, and their goalkicker with a 75 per cent success record so far this season. Losing out on the captaincy to Rocky Elsom doesn't appear to have diminished his desire in the slightest, and the emergence of Quade Cooper as an alternative first receiver has also freed him up to attack wide out.
When it's accepted that there is little enough to choose between him and Dan Carter as the world's best number 10, you realise just how valuable he is to the Wallabies. He passed 500 test points earlier in the year, and is now third on his country's all-time scoring list behind Michael Lynagh and Matt Burke.
With criticism ringing in his ears, this could well be a perform-or-bust day for O'Gara. There could be a slight confidence fall-out following the Lions tour, or simply the sort of dip that affected O'Driscoll this time last year, but whatever the reason, he has been off the pace.
In the past, O'Gara has proved himself time and again to be a superlative big-game player, and this is the sort of test he might just relish. He'll have to cope with the pressure, and with Giteau, but he's done both before.
If the Aussies had problems with the likes of Steve Borthwick pilfering line-out ball for much of the first half at Twickenham, then you wouldn't give them much of a shout against O'Connell.
Rocky Elsom settled things down against England by calling a few throws on himself, but despite the new Wallaby captain's first-hand experience of competing against the Munster pair, this is surely an area which Ireland can exploit. Chisholm is married to Bill Campbell's daughter, and he might just require some of the old Aussie lock's tricks to get him through this challenge. Meanwhile, the massively promising Horwill has already captained Queensland and has played in all of his country's tests this season.
Australia will need their hookers to be at their most accurate if Ireland aren't to burgle some vital possession, however, with John Hayes back on lifting duty, they'll be hard-pushed.
If O'Connell and O'Callaghan haven't had the most auspicious starts to the season by their own high standards, this game is an opportunity to impose themselves on opponents who have less of a reputation and much less experience.
A steady supply of good ball to Will Genia and Matt Giteau will give Australia momentum but sustained disruption by O'Connell and Ireland will be at least some of the way to winning .