One of those two can start at No 10, the other can be direct cover on the bench and Barrett is good enough to be considered a replacement outside back.
The All Black midfield may appear to be already well catered for with Williams, Malakai Fekitoa and Conrad Smith, but that won't diminish interest in having Crotty in the mix.
There may be some interest in seeing if he, at second-five, can form a combination with Fekitoa at centre. Those two, given their age, may become a long standing partnership down the track. An inverse Ma'a Nonu and Conrad Smith - with a ball playing distributor in Crotty and an explosive linebreaker in Fekitoa.
It's possible, too, that the selectors may be wary of fielding a Williams-Fekitoa combination given the relative inexperience of both and they have already said that they aren't sure about using Crotty and Smith together given the relative similarities in their respective skill sets.
So maybe they have it mind to use Williams and Smith as one combination on tour and Crotty and Fekitoa as the other.
With Carter and Williams in and Slade out, it will leave the squad mix at 18 forwards and 15 backs. The 31 players in Brisbane are split 18 forwards and 13 backs (Ben Smith is resting at home but will be named on Monday).
The choice, then, is whether to sacrifice Crotty to to add another forward. They are well covered at loose forward with the six - Jerome Kaino, Liam Messam, Richie McCaw, Sam Cane, Kieran Read and Steven Luatua - that they have. But they may want to take five locks or six props.
If they decide on the former, then Dominic Bird may be called up. If they go for the latter, it may be that Manawatu's Kane Hames - who was on call earlier this year when the All Blacks played in Sydney - is picked.
But it would be a surprise if they don't take Crotty and therefore the only decision to be made in the forwards is whether to keep Jeremy Thrush or swap him out for Bird.
Possible All Black squad
Props: Ben Franks, Owen Franks, Charlie Faumuina, Joe Moody, Wyatt Crockett.
Hookers: Dan Coles, Keven Mealamu, Nathan Harris.
Locks: Sam Whitelock, Brodie Retallick, Patrick Tuipulotu, Jeremy Thrush.
Loose Forwards: Jerome Kaino, Liam Messam, Steven Luatua, Richie McCaw, Sam Cane, Kieran Read.
Halfbacks: Aaron Smith, TJ Perenara, Augustine Pulu.
First-Fives: Daniel Carter, Aaron Cruden, Beauden Barrett.
Midfielders: Sonny Bill Williams, Malakai Fekitoa, Ryan Crotty, Conrad Smith.
Outside Backs: Ben Smith, Cory Jane, Charles Piutau, Julian Savea, Israel Dagg.