David Kelly: Reliance on half-back duo is exposed in their absence
Ireland has already cloned a successful showjumper so why not a champion rugby out-half?
However, Jonathan Sexton, as with pretty much everything he does, is way ahead of the science. He has already cloned himself; you see, there are two Jonathan Sextons. They both look exactly the same and play exactly the same.
Hence, when Sexton starts for Ireland, his side effectively do so with an extra man advantage; trouble is, when Sexton, twice, left the field on Friday, Ireland were reduced in numbers, not to 14, but 13.
Confused much? Let us explain.
The answer is devastatingly simple; if you close your eyes and think, it will be summoned up within your brain momentarily, possibly upon a series of unending loops.
Or wrap-arounds, as the cognoscenti call them.
For Sexton is not only Ireland's most important player - and standing to reason our most important back - he is also a de facto stand-in for the back that Joe Schmidt would love to have, but either has not found or does not trust, in his three-quarter line.
So, as well as being Ireland's most stout defender, Sexton seems to be fulfilling the role of not only an out-half but a playmaking 12 as well.
In the absence of players with a similar passing range outside him, Ireland need Sexton (both of them) to shift the ball closer to the edges.
Analysis shows that when Sexton passes the ball, there is a one in ten chance he will do so again. For every other out-half, the likelihood is closer to one in 50.
It only needs to be effective once; against France it provided the build-up to Ireland's decisive try. It greases the wheels of Ireland's grinding, multi-phased emphasis on retaining possession.
At times, it can be so bewildering that it confuses Irish players as much as the opposition.
But, along with Conor Murray, Ireland's second most important player, Sexton controls and conducts the tempo of the attacking strategy and shape.
World-class half-backs that will, if fit, start against the world champions this summer.
Nobody else in green high numbers will start with them and the riches at the Irish pair's disposal will be stark.
There will be no need for elaborate wrap-arounds, like the overly-complicated, almost dizziness-inducing play that ended up with Rory Best dropping the ball on Friday.
Not if you have another playmaker outside you, a glider at 13 and wheels to burn in the back three.
Ireland currently deploy none of those threats.
Another key stat is that Ireland kick 71 per cent of their penalties to touch as they struggle to break teams down; instead relying on a former strength, the catch and drive.
But that is now a blunt weapon too.
England have a serrated edge; can anyone realistically argue that Ireland do too? There is an absence of pace and guile beyond ten and that is why Sexton is being forced to carry out the labours of two men.
And when he is absent, the consequences are multiplied.
The ten points ceded during the sin-binning - this time after being in defensive mode - were obviously highlighted but the alarming try during his HIA was even more crucial.
Paddy Jackson, look away now. "They attacked well," noted Schmidt, "especially when Johnny went off to get checked out and they went straight through around his area."
"Unfortunately, we lost Johnny and lost a little bit of leadership and you don't need to give Scott Williams too many invitations to break the line.
"He hit a nice line on a good change-up and we weren't quite connected, but it was very tough for Paddy just coming on, to suddenly slot straight into that."
Garry Ringrose reckoned the switch was "seamless" and that Jackson did "brilliantly"; the youngster has not learned to speak his mind yet so his politeness can be forgiven.
Senior partner Robbie Henshaw elaborated more clearly.
"It was pretty tough because we were being kind of pulled and dragged," he says of the try scored immediately after Sexton's first exit.
"Johnny was down, there was a stoppage and then Paddy was in and we were slow to get set and that didn't help our shape in defence.
"We kind of had a bit of a dog-leg coming up in defence and Scott Williams got through on the inside of me, it was difficult at the time because we were out of shape and not in sync."
As if losing one half wasn't difficult enough, striving to operate with the other at half-tilt compounded Irish woes.
Murray's "bravery", enabled by those in charge, was foolhardy and reckless but, as with Jackson, hinted at the extreme reluctance to call for back-up (never mind not doing so at hooker or tight-head prop; four of the changes were made in the final minute!)
Again, Henshaw was bold and forthright.
"Kieran Marmion did exceptionally well in the loose and through the phase-play, but Conor was a massive loss. That was a big moment when they turned us over, Conor had to chase back and they got their try off that maul.
"So, having Johnny in the bin didn't help our shape. We obviously lost a bit of shape in the second half without our main ball-players, we lost a bit of direction as well."
Much has been made, rightly, of the reserve halves' development with Ireland but they have done so outside the cauldron of tournament play, where Ireland have now failed in three successive attempts.
After Friday's catastrophic gamble on him failed, Murray's injury will weaken Ireland further and heap increased pressure on Sexton to take even more of the responsibility upon his shoulders against England.
The stark truth is that this nine-ten axis is so dominant that Ireland simply cannot cope when they are not together.