Slade, the last-minute hero in Brisbane who didn't make the 34-man tour party when it was announced on Monday, had been on stand-by - ready to come in if Carter wasn't able to take his place.
But he has been given permission by Hansen to join the Barbarians, who will be playing the Wallabies in London on the same weekend the All Blacks play USA at Soldier Field.
If there had still been lingering doubt about Carter, Slade would not have been released. As it is, Slade and other recent All Blacks Steven Luatua, Matt Todd and Dominic Bird, who are also playing for the Barbarians, will delay their travel home after the game.
They will wait in London to see if the All Blacks pick up any injuries in the States.
With Carter now likely to be on the plane, the next task for the selectors is working out how best to use him and how much to use him on the tour. They are conscious that after taking a six-month sabbatical in the early part of this year, he managed only five games - 297 minutes - at second-five for the Crusaders before he broke his leg in the Super Rugby final.
He looked sharp and full of running on his return and his extended time off had allowed him to clear all the niggles that had plagued him since late 2011.
Carter had originally hoped after breaking his leg in the Super Rugby final that he would be fit enough to play for the All Blacks on their away leg of the Rugby Championship.
But his leg took a little longer to heal and the decision was made that he should return to test football via the ITM Cup. His first game back was for Canterbury against Southland on the same weekend the All Blacks played Argentina and he managed 40 minutes where he was composed yet clearly playing a little within himself.
He took a blow to the shin in that game which he has been struggling with for the last three weeks. It wasn't a major collision but it highlighted that his nerves still hadn't settled and that while he could train fully, he couldn't handle contact without discomfort.
The All Blacks have two class alternatives at No10 in Beauden Barrett and Aaron Cruden, but they are eager to get Carter back at the helm as they believe once he's back in his best personal form, he can drive the All Blacks to a higher collective performance.
Despite his lack of game time in 2014, a player of his ability and experience will probably be trusted to start against the US and be given 45 minutes to 55 minutes to get himself re-accustomed to the pace and intensity of test football. The bigger decision will come the following week and whether they are prepared to start, or even have Carter on the bench against England.
3 Things about Dan Carter
1 Minute-man
Carter has played a grand total of 337 minutes of rugby in 2014.
2 100th the last
His last test was against England - his 100th - at Twickenham where he limped off after 25 minutes.
3 Still on high
He remains the highest points scorer in test history with 1442.
