Carter was ruled out of the tournament last week after he suffered a groin strain during kicking practice.
Despite the loss of their talisman, Henry believes that the inexperienced Slade will step up to the mark.
"I've been pleased with him - I think he's getting better. He's getting more comfortable in the group. He's obviously the navigator of the team playing at 10, he's got to run the ship.
"And that's a big ask when he's playing with guys who have played 100 Test matches and 75 Test matches and so on and he's played 10 at most. It's a big ask for him, but he's getting more comfortable, he's enjoying the environment - I think he'll play well."
Vcitory at this tournament on their home soil would mark the All Blacks' first World Cup triumph since 1987.