In 2012 it was Cruden, having been an All Black since 2010, who was the designated heir apparent. He had the experience and exposure to test football which Barrett didn't.
Cruden was, to some degree, proven having played in a World Cup final and on that basis and given that he was still only 23 in 2012, the obvious projection was to see him as Carter's greatest threat.
And that proved right in that Cruden was picked at No 10 for the first tests of 2016 after Carter had retired.
Up until then, he'd held off the threat of Barrett, who for all his outrageous skills, hadn't managed to prove himself as a test first-five.
It wasn't until later in 2014 that Barrett actually first wore the All Blacks No 10 jersey and in the end, he just wasn't given the length of time in the role that he required to press his case.
He came into 2016 as a brilliant bench option and the big question was would he ever transition from that into a starting No 10? The answer came when Cruden damaged a knee in the second test of the year and Barrett has never looked back.
He won the race hands down in the end and the future is all his.
The fact Sopoaga began 2016 with a test under his belt in a sense makes him the equivalent of Cruden.
He's the favourite at this stage and certainly, in the last few games, he's established his qualities. He's a good player and showing the right sort of temperament to thrive at this level.
He would have started this weekend in Argentina but for the birth of his first child and now, probably, McKenzie may enjoy a 20-minute run there later in the game.
And that will be the first sign that the race is starting - a reminder that the long-term future of McKenzie is as a No 10 and not as a fullback where he has played all of his tests so far.
No one has quite been sold on him at fullback during the Rugby Championship. He's been equal parts good to not so good with this permanent sense that it's just not the right role for him.
But give him a season at No 10 for the Chiefs next year and the picture could change entirely.
All of a sudden he'll be like Barrett, a fast-rising force who may, in fact, be the real heir apparent rather than Sopoaga.
But unlike Barrett, McKenzie could make his run in time to pip Sopoaga before the next World Cup.