A long-term injury to Anton Lienert-Brown has put the spotlight on the All Blacks' midfield stocks for the upcoming schedule, with Foster admitting they were a concern for him and his selectors.
Quinn Tupaea of the Chiefs and David Havili of the Crusaders firm as candidates to fill the All Blacks No.12 jersey, already boasting midfield experience at test level, but a solid, if not unspectacular start to life with the Blues may also see Tuivasa-Sheck answering those questions.
The 28-year-old has continued to develop this season, as the team sealed top spot in the Super Rugby Pacific and a club-record winning streak of 13 matches.
All Blacks great Sir John Kirwan has already put Tuivasa-Sheck's name forward for a test spot, while Foster himself acknowledges the work of the former NZ Warriors captain.
"We're pleased with Roger's growth," Foster told the All Blacks podcast.
"Particularly defensively, he looks reasonably settled. It doesn't mean he's getting everything right, but he looks reasonably settled.
"He's certainly good on the carry stuff. He's probably still learning how to link and get the passing game.
"I'm not sure about the state of the kicking game, because I haven't seen it yet.
"He's an outstanding guy, he's doing a great job with the Blues and we've had some connections with him.
"I know he's in a great spot. We've just got to look at his progress, particularly the next 4-5 weeks will be critical in that."
Another contender could be Jordie Barrett, who shifted into the Hurricanes midfield this season.
Barrett, 25, stood out for the All Blacks in 2021 to cement his status as Foster's go-to fullback, but was required elsewhere in Super Rugby this year.
And while Foster outlines exactly where he'd prefer to see Barrett playing in his side, the option of another utility player is one the All Blacks will always welcome.
"We've watched with interest, him playing 12," Foster added. "To be honest, it hasn't excited me that he's gone into there, but that's OK.
"The way I see it is that he's played 12 before, he quite enjoys it. If it stimulates him, that's great.
"I'm interested to see what it is, whether it's an option for us long term, because it might become one, but the clue that I'd give you is that I thought he was one of our best All Blacks last year - his goalkicking, his high-ball stuff, kicking stuff.
"If you start thinking about World Cup stuff - France, big stadiums, high risk, low risk teams playing - you have to have a back three that defuses high ball, has got a great kicking game and is strong defensively.
"He ticks those boxes. I still love him as a 15, but are we willing to consider some option at 12? Yes we are."