The Springboks nearly completed a stunning reversal, coming agonisingly close to victory against the team which smashed them 57-0 at Albany.
The All Black coach said he had "rolled the dice a bit" in an effort to leave more petrol in the squad's tank for the end-of-season northern hemisphere tour.
It almost backfired though. The All Blacks were taken to the wire by the Springboks, with the young outside backs coming to the rescue after the forwards copped a battering.
Sam Whitelock, Sam Cane, Liam Squire, Ryan Crotty and Lima Sopoaga bypassed the test in Buenos Aires. Cane and Sopoaga were noticeably sluggish, while Whitelock seemed to fade after a big start.
Hansen indicated at least some of them were off their game in Cape Town.
"Why we did that was not so much for here, but for the end of year( tour)," he said.
"They hadn't played for three weeks, and were probably half a game short. We saw that in their performance - they were a split second off where they are capable of being.
"They felt that themselves, talking to them afterwards. Hopefully we'll get the benefits of doing what we've done somewhere like Cardiff."
Meanwhile, Beauden Barrett's immediate playing future seems unclear, after the All Blacks kept him on the sideline even though he passed a head injury assessment during the test.
"He just felt nauseous and made the comment he had stars," Hansen said.
"If you've been concussed that's one of the symptoms. We felt it was not worth him going back there. He was pretty good today. We've got a couple of weeks and see how we go."
Hansen confirmed Nehe Milner-Skudder will be out for about six months, requiring an operation after dislocating his shoulder in the Cape Town test.
"He's well versed in what has to come...it's the second one he's done, he had one on the other side," Hansen said.
"He knows he can get the recovery done. He hasn't had much luck, poor bugger.
"But he's playing well and it's a good time of the year for it to happen I guess . . . he wouldn't have been playing for some of those months."