The All Blacks, who name their 31-man World Cup squad next week play Tonga in Hamilton on September 7th before facing South Africa in their opening Pool B clash two weeks later.
Hansen said he was wary of his first-choice players losing sharpness between last weekend's 36-0 victory over Australia at Eden Park and their World Cup opener.
"We'd like probably most of the frontliners to get some form of game-time in the Tonga game, otherwise it's too big a break before we play South Africa," Hansen said in comments published by Stuff Media.