Captain Paul O'Connell doesn't doubt Jonathan Sexton's ability to come through a different kind of head test against France.
The Ireland out-half will definitely be targeted by the French as a possible point of physical weakness after twelve weeks out of the game from multiple concussions.
This is where Sexton and his predecessor in the position are different. Where Ronan O'Gara had to have David Wallace there as a minder of sorts, Sexton is a bigger, more aggressive proposition.
He doesn't need back-up, does he? "I think it is the last think he would want to think or he would want said about him," said O'Connell.
"Johnny is very enthusiastic about D (defence) within the camp, about line-speed, about knowledge of your roles.
"You know he is a leader in every regard but particularly in that regard. Yeah, the 10 channel is something that is always attacked."
When the French come there, Sexton will be ready to put body and mind on the line.
"In terms of defending and the way we defend at the moment, if someone comes into your channel you have to make your own tackles.
"You'll have a guy outside you and inside that will look after you and help you but you know everyone all across the park one-to-fifteen is expected to make your own tackles."
The traffic will be large, articulated and moving at a fair lick as Les Bleus will look to turn on the power game.
This is nowhere better encapsulated than in the fabled figure of their beastly centre Mathieu Bastareaud.
"He is a very powerful man and you have to tackle him low, you have to chop him low," reviewed O'Connell.
"He is excellent over the ball. He is kind of like Steffon Armitage. Once he is clamped over the ball he is very hard to move and he regularly gains points and territory through penalties for his team.
"He is a guy we prepare for. You have to prepare quite specifically for him because he is a very different threat to other players.
"We prepare for the very best of what they are going to bring. He has been playing excellent both for Toulon and for France in recent months."
Of course, Ireland can undermine France's confidence by getting out to the kind of start they managed against South Africa and Australia in November, not the kind that kept Italy a live threat until Conor Murray's 62nd minute breakthrough try in Rome.
"I think one of the big things last week was how we started the game," O'Connell recalled.
"You know, you have to start these games well and that was a disappointing aspect of last week's game, in terms of giving the team confidence after having not been together for so long.
"So we'd be eager to start well, eager to be a little bit more accurate in terms of what we do obviously.
"It's probably something I'd say and everyone says at every press conference, you have certain plays you want to execute and you want to do them right.
"You want people in the right place so they can perform their roles really well, and that goes to defending as well, it goes to kick-chase, it goes to our set piece.
"I think accuracy will be a big thing, you have to be ready for a massive physical challenge.
"The French are big. They're strong. They're powerful. I think they're well able to use it and put it about and we need to step up that physical part of our game considerably."
Ireland's defence is rated one of the best in the game, their penalty count is generally costed in single digits.
It is confidence in the man either side of each individual that allows a player to do his job without having to worry about someone else.
The element of trust leads, in turn, to better discipline because Les Kiss's scramble system has been shown to work under severe stress.
"A big part of it is in training, it is treated the same as matches in terms of our discipline," the Irish captain said.
"You don't get away with any silly infringements in training and that is something we emphasise, Joe and the coaching staff emphasise quite a lot whether it's lineouts, whether it's gaps in lineouts or whether it's the scrum, the back foot at the ruck.
"Those habits permeate through onto the pitch," he claimed.
"Every team prepares for the referee. You try and give him the best possible pictures that you can and that is how we do it.
"I suppose the big realisation is what it does to the team as well. Penalties in rugby are so destructive, they take away your momentum.
"They give massive momentum to the other team. It's either three points on the board or it's 50 metres down the field.
"We are well aware of how important that part of the game is."
Ireland: R Kearney; T Bowe, J Payne, R Henshaw, S Zebo; J Sexton, C Murray; J McGrath, R Best, M Ross, D Toner, P O'Connell (capt), P O'Mahony, S O'Brien, J Heaslip.
France: S Spedding; Y Huget, M Bastareaud, W Fofana, T Thomas; C Lopez, R Kockott; E Ben Arous, G Guirado, R Slimani, P Pape, Y Maestri, T Dusautoir (capt), B Le Roux, D Chouly.