Steve Hansen loves Damian McKenzie's aggression, but has challenged him to make better decisions in the test arena.

All Blacks first five-eighth Beauden Barrett has backed rising star Damian McKenzie as a quality fullback, saying he can see a bit of himself in the 22-year-old.

McKenzie took a hold of the black No 15 jersey during this year's Rugby Championship as injuries struck fullback rivals Israel Dagg and Ben Smith, who was now out of contention as he took an end of year break from rugby.

Young talent McKenzie has taken his chances, impressing with his running game - especially in broken play, which was a key to Barrett's breaking onto the world rugby scene as a charged-up fullback playing in a backline directed by first-five great Dan Carter.

David Rogers McKenzie retained his place at fullback in an All Blacks starting XV to face France.

Speaking from the All Blacks camp in Paris ahead of this weekend's test against France, Barrett backed McKenzie as the team's fullback.

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Jordan Mansfield Steve Hansen says McKenzie is challenging Jordie Barrett for the backup fullback job behind Ben Smith.

"He sometimes reminds me of my younger self," 26-year-old Barrett said of McKenzie.

"I get excited every time he gets the ball because I know what he can do, but he's going to get better and better just by experience."

MCKENZIE WORK-ONS

During his day off in Paris on Wednesday, McKenzie negotiated the notorious Arc de Triomphe roundabout on a pushbike. It was an action not without resonance, as his All Blacks coach wants him to find similar order among the chaos of a test match.

McKenzie, as expected, retains his place at fullback in an All Blacks starting XV to face France on Saturday night (Sunday NZT) featuring three changes from Brisbane three weeks ago. Beauden Barrett is back to run the show at No 10, Vaea Fifita steps into No 6 for the ill Liam Squire and Luke Romano is preferred at lock ahead of Scott Barrett who drops to the bench.

McKenzie's selection was a no-brainer, as the smiling assassin from Waikato, by way of Invercargill, has largely made an excellent fist of the No 15 role since stepping in for the sabbatical-taking Ben Smith and injured Jordie Barrett. He has started the last seven tests on the bounce.

But in Brisbane there was just a hint that among that wonderfully instinctive, risk-taking freedom with which he plays lurks some questionable judgment. All Blacks coach Steve Hansen used the fly in a bottle metaphor then, and rehashed it this week in Paris when talking about the adjustments they want to see from their compact but expressive No 15.

"I've said he's like a fly in a bottle and he's getting better at that. He's not hitting the sides so often now," explained the All Blacks coach.

"He has to learn how to play test rugby and test rugby is not like Super Rugby where you can do audacious things and get away with them.

"We don't want to stop his flair, but he's got to get better at the risk and reward concept of what he's trying to do. He's still learning, but he is an exciting prospect."

Hansen says McKenzie has got to a point where he's now challenging Jordie Barrett for the backup fullback job behind Smith, but confirmed they retain a more fluid vision of his future role.

"We'll see him at 10 all next year in Super Rugby which is going to be exciting. Deep down in my heart of hearts I think that's where he'll end up playing most of his rugby."

McKenzie isn't thinking his future just now. He's got a Brisbane defeat, and a flea in his ear around option-taking that didn't best please his coaches, to erase.

"Coming off a loss you want to get straight back out there and prove yourself again," he said. "It's been a long three-week wait. It was my first loss in the black jersey, and took a while to sink in. It was a good learning."

That learning?

"Just around my option-taking, what's right and not right, and being smart around my footy. At times I like to take a few risks, but it's trying to get that balance between high risk and high reward.

"It's not about changing anything dramatically, but improving the little things, the most important things. I learnt a lot that game."

On Wednesday in this beautiful city he went on a cycle tour that took in the Louvre, the Notre Dame cathedral and that Arc de Triomphe circumnavigation that requires a mix of bravery and fine judgment.

"It got the heart ticking over for a couple of minutes," he said of the roundabout. "The driving is a bit different in Paris compared to back home. I don't know if there are any rules over here. You just drive where there's space."

No rules. But one important rule. A bit like how Hansen wants him to play his rugby. Cut loose. But not too loose.