With due respect to Tonga, Fiji, Australia and Argentina, the Springboks were always going to provide the litmus test for the All Blacks.
Setting aside their great rivalry, and the occasion surrounding last week's 100th Test, the Boks are the antithesis to the All Blacks.
Where the Wallabies and Welsh, under Wayne Pivac at least, Fiji and others embrace attacking flamboyance and fast-paced phase attack, the Boks are the turtles of the rugby kingdom; slow-moving, stubborn with a near impenetrable shell that makes them extremely difficult to breakdown.
The turtle comparison certainty fits the constant stoppages the Boks impose on the game. "It did get very frustrating," All Blacks prop Joe Moody said. "It felt like I was hardly getting a sweat on. Just about every stoppage someone was going down and having a smoko. It'd be nice if something could be sorted by the officiating this weekend."
While the All Blacks emerged on the right side of last week's historic Test ledger, thanks to Jordie Barrett's clutch late strike, in many ways they failed to cope with the contrasting pressure the Boks bring.
After largely cruising through the Bledisloe Cup and Rugby Championship - eight points their smallest margin of victory - the All Blacks copped a stark reminder from the Boks that the Test arena can humble you at any time.
Loathe the Boks style all you want - even former captain Jean de Villiers agreed it has gone too far in shunning any form of attack - yet the basic premise of smothering, frustrating, physically dominating the All Blacks succeeded in spades in Townsville.
As All Blacks forwards coach John Plumtree explained, the blunt and brutal review this week laid bare issues at the breakdown, under the high ball, in the collisions, at the lineout and with the backline attack being too flat and therefore failing to identify space.
Shut the All Blacks down at the source, and half the job is achieved.
"Our breakdown work wasn't anywhere near the standard it needs to be against the Springboks," Plumtree said. "We couldn't build enough pressure because we were turning too much ball over."
Facing the same opposition, and highly likely mirror image tactics, should allow the All Blacks to make major improvements in all aspects for their rematch on the Gold Coast. Reducing their 23 turnovers would be a good start.
If rectifying those issues isn't enough motivation Foster has dangled the 'grand slam' carrot - claiming the All Blacks' fifth unbeaten Rugby Championship since the tournament's inception in 2012.
After finishing last year, Foster's first at the helm, with a 50% win record during a COVID-affected six-Test campaign, notching 10 straight wins would be a notable achievement indeed.
The Boks will, meanwhile, be keen to snap their first three-match losing run since 2016, having been stunned twice by the Wallabies.
While the Boks seem oblivious to criticism of their dour style, one suspects another high ball barrage alone won't be enough to cripple the All Blacks again.
Assessing the All Blacks at this point is difficult. How they adapt and adjust to the flaws the Boks exposed will shed a revealing light on their evolution under Foster to the mid-point in this Test season.
Perspective is required, though. The All Blacks have tackled the Rugby Championship without several world-class leadership figures - Sam Whitelock, Sam Cane, Dane Coles, Aaron Smith and Richie Mo'unga, who is expected to return off the bench this week after completing two weeks in hotel quarantine, among them.
Remove five comparable figures from other Test nations, and they would be on their knees.
Foster, while continuing to bank wins, has built impressive depth in most positions this season.
Consider Samasoni Taukeiaho's emergence at hooker, Ethan Blackadder in the loose forwards and 21-year-old lock Tupou Vaa'i's progression. Sevu Reece was left out the past two weeks; Damian McKenzie can't crack the starting team and Dalton Papalii and Anton Lienert-Brown have battled hamstring injuries.
Of the absentees, Smith's has been particularly telling. Replicating his experience, speed to the base, crisp pass and sound decision-making is impossible.
Much of the focus for the rematch will fall on whether the All Blacks can deal with the inevitable aerial assault. When confronting the Boks, though, All Blacks prop Nepo Laulala knows there's one area where the battle starts and finishes.
"When you come up against a pack that just want to kill you, just want to go straight through you, it's a different feeling, especially after the game," Laulala said. "They're big strong men who want to fold you in half.
"They're a natural brick wall when you try to run through them. It's always an arm-wrestle against the Africans, but these are the games where you clearly see what you need to work on as well. It was tough and way more satisfying than these big winning-margin games."
As far as offering a true gauge to where Foster's All Blacks are at, this week will be more revealing than any in the past two years.