Barrett is a brilliant player and in the top layer of All Black pivots but has been struggling to find a better tempo to his recent work.
Perhaps it's the game plan, the ball delivery, the opposition defiance or an amalgam of those factors but the team flow and Barrett's snap have been patchy.
In South Africa there are similar barbs being aimed at Jantjies after a patchy performance in last week's stalemate against the Wallabies.
That match has blurred a season when he was strong for the Lions in Super rugby, solid in the series win against France and twin Rugby Championship victories against the Pumas.
Questions remain about Jantjies' ability to cut it at the top level, issues which are sidecar passengers to every No10's motorbike.
Famous Springbok five-eighths before him, Morne Steyn, Henry Honiball, Joel Stransky and Botha all weathered periods of criticism and praise. As so many coaches have said, it comes with the territory.
Departing Lions coach Johan Ackermann mentored Jantjies and said his impact was similar to Barrett's when he was given the freedom to play rather than operating under stringent instructions.
Those comments suggest when the grind is on in top-level tests where the pressure gets tighter and the margins for success are reduced, Jantjies' form and decisions can waver. That scenario played out in Perth in the 23-all draw with Australia. Jantjies' response tomorrow will be one key area for the Boks in their attempt to reverse recent results against their hosts.
Midfield defence, scrum connections, tactical appreciation from the back three - the list of fix-it areas for the Boks is broad.
However, they are on a stronger flow than their poor 2016 performances.
This is a step up for them - probably more of a hillock - and coach Allister Coetzee who is working to find the methods which best suit his players and their skills.
The Boks missed the mark last year but have tuned their tactics, picked form players and attacked games.
The All Blacks are not on top of their game but are better than most at scratching out results when they are under the cosh.
If they find the right mixture at Albany tomorrow night, Barrett will be tough to handle but if the Boks push in front and limit their mistakes then they will look to Jantjies to help turn the screw.