Concussed All Black Smith out of Lions series
Smith left the field early in the first Test last week and although there were no long-term effects, Hansen said he was taking a conservative approach to Smith's return.
"Long-term concerns have been allayed, but we're just going to take our time with him and get him back to where we need him to be, so he's comfortable, we're comfortable," Hansen said.
"It's too important for him and us in the game to chuck him back out. It's just not worth it."
Smith had already been sidelined twice with concussion in Super Rugby this year and "we're just of the opinion that he's had a couple so let's just be a little bit conservative and not play him".
In a backline reshuffle, Israel Dagg will replace Smith in Saturday's second Test in Wellington with Waisake Naholo taking Dagg's place on the right wing.
Dagg said he had been in contact with Smith and felt for the 62-Test fullback who would be missed in a clash the All Blacks want to win to wrap up the series with a game to spare.
"But at the end of the day he's got two little kids and a beautiful wife. You just have to make good decisions," Dagg said.
"It's only rugby. We've got a life after footy to worry about. For him, he's had a few head knocks this year so he's made the right decision.
"Gone are the days when you think you're Superman and strong and just get up and run around and think these things don't affect you. You've seen the research, you've seen what happens."