NZR must tread carefully with All Blacks coaching decision: Hansen

Foster's contract runs until after the World Cup in France and while the 57-year-old could apply to stay in the job a poor run of form earlier this year has made Canterbury Crusaders coach Scott Robertson the favourite to take over.

Hansen said NZR are caught between a rock and a hard place, knowing that they could lose their preferred candidate if they wait too long but may also alienate Foster by announcing a decision before the end of his contract.

"If you're going to name a new coach before the World Cup's over, then you've got people looking at who is the boss and looking at two different people. That is a possible derailer and you don't want that," he said.

"They need to sit down and if they make a decision to do it, they would have to put some boundaries around what the incumbent coach could and couldn't do.

"Basically I think he should be told, then leave it at that until such time as the World Cup is over and then announce it."

Hansen, who led the All Blacks to World Cup glory in 2015, said naming a successor to Foster while he is trying to guide the team to the title in France would create problems.

"You don't want someone distracting, because he's ... all excited and starts having conversations that aren't necessarily until after the World Cup," he said.

"The ironic thing is that if they win the World Cup, what do they do with Ian Foster if they've already appointed someone? So they're in between a rock and a hard place."