Allen was a gifted and skilful first-five who played nine games for the All Blacks in 1980, including two tests, making his debut at the age of 21. But the former Auckland and Counties representative was hindered by injury throughout his senior career and tragically died aged just 26 from a head injury suffered while playing club rugby in Australia.
Barrett is so often the topic du jour in the build-up to an All Blacks test because the 25-year-old has erupted into the most astonishingly consistent and devastating form.
He's the man who can do no wrong and while he's been by no means exclusively responsible for taking the All Blacks' attacking game to a new level, he's certainly been instrumental in that. His running game has been the show stealer. He's so often found a way to hit the line at incredible pace and scorch through holes. The defining image of this year has been Barrett, coming from deep on an angled arcing run, coasting past defenders who simply can't cope with his speed.
But from Hansen's perspective, the most pleasing part of Barrett's development has come in his game management and overall decision-making. Building that side of his game was always the priority and while Hansen always had faith that Barrett would advance his work in that area this year, the coach admits to being pleasantly surprised at just how far the young No 10 has come.
Far enough to say that Barrett has surpassed expectations?
"Yeah, probably, if we are being fair," says Hansen. "He has got there a bit quicker than we thought and I think that is helped by the Hurricanes playing right through that period, the quarter-finals, semifinals and final.
"He has been exposed to that pressure and having to drive his team around the park. If you think back to the weather conditions, they weren't the best and he really had to step up and own that and he did that well and has taken some real confidence out of that, and that has allowed him to take his game to another level.
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"We know he has a great running game but having that confidence to step up and drive the ship the way he has, he has improved his game."
There is, though, a cautionary element to Hansen's praise. Barrett has come along in leaps and bounds but there is still plenty of room for improvement. His goal-kicking sits well below Daniel Carter's 80 per cent test average. There's also a desire to see whether Barrett can be the same figure of influence if the All Blacks aren't inundated with quick ball.
Against the Wallabies, around 50 per cent of their possession was deemed to be quick enough to use. In past games against the Pumas, that figure has sat around 35 per cent and if it is the same in Hamilton, Barrett will have to show he has the patience and control to play his side into the right places and pick and choose when to unleash the wide-wide passing game that destroyed Australia.
It has been a huge season for Barrett but the Pumas present him with the toughest challenge he has faced so far in 2016.
