All Blacks selector Grant Fox, a former first-five who played 46 tests, said Barrett had proven himself on the biggest stage when replacing Dan Carter during the first half of the 29-15 Rugby Championship victory at Eden Park.
Barrett challenged the Springboks' defence time and again with his ball carrying, tackled as well as he ever has, and generally took control in a match in which both teams occasionally crossed the line in terms of foul play.
However, Cruden, who hasn't played since starting in the Bledisloe Cup I victory over Australia on August 17, remains Carter's No1 back-up. "On the basis of one performance, whether the guy plays really well or not so good, we don't change our minds, we don't chop and change," said Fox.
"What we're really pleased with is Beauden's growth, so we're just developing real depth in the No10 jersey. You go back a little while, we were all concerned when Daniel got hurt ... It was a collective thing, there was a fair gap to Dan and the next and that was Stephen Donald.
"Now we are comfortable that we have the world's best 10 and he has been for some time ... and we've got another guy called Aaron Cruden who, if he isn't world class already, he's nearly there. And we've got another young man who is starting to make his mark as well."
All Blacks coach Steve Hansen and his fellow selectors have shown a willingness to stick with continuity which means there is unlikely to be too much tweaking to the team which will take on the Pumas at La Plata a week on Sunday. The final game of the championship, which they lead, is the return encounter against the Boks at Johannesburg a week later.
Cruden ran fully and tackled at the All Blacks' training on the Thursday before the Boks test so is likely to be available for selection, but whether he starts or comes off the bench will depend on his overall fitness, Fox said.
For Fox, Barrett's efforts in the biggest test of his career was a sign that his confidence is finally where it needs to be and was foreshadowed a day earlier when he effortlessly took control of the backline when replacing Carter at the captain's run.
"This young man is growing and we've seen that in the last 12 months. He is still a very young guy at 22 years of age and when he first came in he was a bit shy in our environment which is understandable. But now he has grown in confidence to the point where now we know when he steps in he will take over and run the cutter.
"He knows he's good enough to be here and that's a big step because when you first get the opportunity, mostly when you prepare you're full of doubt. That's natural, you're nervous as hell, 'am I good enough to be here, can I foot it on this stage', and it takes time to get comfortable."
Fox said Hurricanes' pivot Barrett has always had the ability to take on the defence and his tackling was improving all the time.
"He's actually a big lad, bigger than you realise. He's quite tall but he's rangy. He's still going to fill out yet. He's a brave young man, he's not afraid to take the line on and he's bloody quick too."
All Blacks No10s, in order
1. Dan Carter (age: 31, tests: 97)
2. Aaron Cruden (24, 23)
3. Beauden Barrett (22, 11)
4. Tom Taylor (24, 1)
5. Colin Slade (25, 11)
Pivotal injuries this year
Carter: Broken hand, strained calf, shoulder joint (unavailable for two of three France tests and two Bledisloe Cup tests. Now out for rest of Rugby Championship)
Cruden: Knee (ruled out of Bledisloe II and Argentina and South Africa RC tests)
Barrett: Calf (ruled out of Bledisloe II)
Taylor: Ribs (injured in Bledisloe II, now back in squad)
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