The 17-test midfielder confirmed in February he will head offshore at the end of this Super Rugby season.
And despite Hansen admitting to initial disappointment and frustration by the lack of communication around Kahui's decision, the All Black coach has made it clear the New Zealand mantra remains centred on picking the best team possible.
Kahui says that's encouraging, but he's well aware that spending two years overseas still remains dangerous when it comes to hanging on to an All Black jersey.
"They're very open to foreign players coming back, but there's a huge risk factor for guys that go away," he said.
"The level of rugby, while it's not bad, is not Super Rugby, and you can easily fall behind with your skills."
The versatile 27-year-old Chiefs back said the lure of the 2015 World Cup provided a strong incentive to keep at his best.
"If it happens I come back and give that World Cup a crack, I'm going to have to make sure over the time I'm away that I'm playing really well and working hard in the gym and other areas so I don't fall behind."
Hansen said last week that the All Blacks' policy around players on overseas contracts was clear.
"You've got to be playing in New Zealand and I agree with that policy. We've got no problem with them leaving, and no problem with them coming back," he said.
"Our primary role is to pick the best side we can. If Richard is playing out of his skin, and by far away the best player in his position in the country, then we're duty bound to pick him.
"But if he's only playing as well as someone else, and that someone else is staying in the country, then we've got to make a decision for the future."
