Johnny Sexton: 'I've been away for 12 weeks and I did feel a bit rusty at times'
Ireland's most important player can bring Schmidt's vision to life
The loss of Jamie Heaslip to Ireland is not insurmountable. The loss of Jonathan Sexton would be.
That is how central the out-half is to the game plan of Joe Schmidt.
The best fly-half in Europe, arguably the world, is to the Ireland backline what Paul O'Connell is to the forward eight.
Just more important.
Where captain O'Connell can lift the standards of all those around him through his presence and his unbending dedication to the cause, Sexton is the most influential because he is the goal-kicker, the general, the quarterback, the points builder.
The fact Ireland were able to reclaim four of their five restarts against France, by forcing a spill, snatching the ball up as Robbie Henshaw did or driving Damien Chouly into touch as Seán O'Brien did was all down to the pinpoint accuracy and hang-time of Sexton's boot.
And this is just a minor, but significant, detail from an evening of a thousand details to be read, felt, executed on his return to the international arena, or any arena for that matter, for the first time in twelve weeks.
This is why Ireland coach Joe Schmidt will watch Racing Metro's Top-14 match against Clermont-Auvergne on Saturday night in Paris through wincing eyes.
This one won't be for the feint-hearted as Racing, in fourth, host second-placed Clermont, one point behind leaders Toulon.
So much of what Ireland implements revolves around the kicking of their half-backs Conor Murray, from the base of ruck and maul, and Sexton from everywhere else.
Racing's controller-in-chief feels he owes his club a debt of gratitude and game time and his country finer-tuned skills.
"Well I need game time, don't I?," he said, about the prospect of playing this Saturday.
"I think I've been away for 12 weeks and I did feel a bit rusty at times, so I think I'll be better with another 50 or 60 minutes, I'll be better the week after for that.
"And then we play England."
It is a measure of his exacting standards that he slipped two of the few mistakes he made into the conversation rather than the five-from-five kicks, the stupendous defence or the all-round accuracy.
The interesting point is he made an unsympathetic face-hitting pass to Jared Payne and took a clash of heads with Mathieu Bastareaud because he was trying to limit what could go wrong.
First up Payne: "I maybe could have gone over the top to Zebs (Simon Zebo), but, at the back of my mind, I'd (Yoann) Huget, a massive intercept threat.
"Even the other time I got hit by Bastareaud, I suppose I was a bit worried about throwing that ball close to the line when they are liable to shoot, (Wesley) Fofana was there at that stage."
Maturity and experience have combined to give Sexton the panoramic vision of measuring in a split-second what could go wrong against what could go right.
"Yeah we'll have a look at it, there were a couple of opportunities there that we needed to take and we'll need to take against England."
That is why Sexton and Ireland would be better served by him playing for Racing on Saturday.
The reality is that Schmidt does not have the magical Brian O'Driscoll at centre outside his telepathic buddy Gordon D'Arcy.
He has Robbie Henshaw's athleticism, power and sponge-like capacity to learn and Payne's clever footballing brain and improved physicality.
They have now played together twice for Ireland in the Six Nations. This is a relationship that has to be nourished slowly, surely. Schmidt is limited in what he can create there simply because of their unfamiliarity. That will change in time.
The New Zealander doesn't have blinding speed around the outside either with Tommy Bowe and Simon Zebo, not compared to what is available to Stuart Lancaster at England.
He does have the Ulster man's timing onto the ball, height and high-fielding Gaelic skills on the right and the Munster man's footwork and change of pace on the left.
For all of this, Sexton is the main ingredient in getting the ball to all four men in situations that play to their particular sets of skills.
When the Irish pack needs respite from the hand-to-hand combat that predominates the Six Nations against much bigger men, they look to Sexton to take them forward to apply pressure, get into their lineout-maul or strike quickly from first phase.
Sexton gives Schmidt all the options to plan for what is ahead of Ireland and how to best overcome England.