Keith Duggan/Sideline Cut: It is becoming impossible to separate the rugby lives of Ronan O'Gara and David Humphreys. News that the Corkman would take possession of Ireland's number 10 shirt for tomorrow's match against France created an instant surge of excitement accompanied by a simultaneous pang of regret for the Ulster man.

For all the talk about how blessed Irish rugby has been with two high-calibre outhalves, the situation is as potentially dangerous as a loaded gun. The pair have been skilfully portrayed as a dual alliance, a complementary force, but every athlete has to believe in his or her pre-eminence and, from that perspective, both men have been engaged in a duel for the rights to the number 10 jersey for the past three years.

That this internal competition has not produced even one intemperate comment or ever threatened to create disharmony in the Irish squad is due in no small part to the unfaltering and constantly self-searching philosophy that both players bring to their game.

It must also be partly attributable to the shrewdness and caution that is at the core of every Fast Eddie O'Sullivan move.

The pair provide a number of classic sporting choices: youth versus experience, hot confidence versus coolness, improvisation versus technique, Munster versus Ulster, the brooder versus the reasoned. And yet although preferences have been expressed for one player over the other, never are they gung-ho. It has been impossible to ignore the qualities of the player-in-waiting.

Ireland's trick has been to nullify the debate by calling on the skills of both in so many key matches. O'Sullivan has managed to seamlessly switch to O'Gara as first-choice outhalf as the World Cup reaches meltdown while eluding the natural conclusion that Humphreys has been "dropped".

The Ulster man will almost certainly appear at some point against France and - as with his sweet and brave and missed drop-goal against Australia - could yet have the defining say.

The contest between the players, the range of their gifts, remains so tantalisingly appealing that merely starting does not necessarily imply first choice. With the exception of Ireland's Grand Slam whipping by England, recent games have been so tight that the outhalf who finished the game has had just as important an input as the starting player.

Because of age alone, O'Gara represents the future of Irish rugby. It must be true, though, that his exposure to Humphreys in the full autumnal vintage of his career and the spirit of their competition at international level has been of enormous benefit to the Corkman.

When you think about it, their relationship is extraordinary. Given an unlikely opportunity to start for Ireland in the last Six Nations because of injury to O'Gara, Humphreys took it as a sign from the gods and in Murrayfield played with an almost childlike abandon. It was a new side to a player so often perceived as a worrier and a perfectionist. That evening he spoke candidly about the basic joy he felt at being able still to play for Ireland and about how he would treat every game as his last.

From that day on, O'Gara must have known he would have a fight in his hands to restore himself to the team ahead of the World Cup, and so it has been.

And yet, O'Gara's contribution has been astonishing. For some reason, his winning drop-goal against Wales in Cardiff seems to have fallen into a black hole in terms of public recognition. Not only was that one of the great moments in the televised history of Irish rugby, it ranks as one of the true operatic passages in the entirety of Irish sport.

The moment shone with everything you could possibly ask from sport. The Millennium stadium was, remember, still in absolute happy chaos from the majestic drop-goal Stephen Jones had landed just one minute earlier. Not only was O'Gara kicking to win a massive, season-defining game, he was dealing with the added pressure of trying to top a brilliant kick in a crazy environment. It was truly heroic.

After the loss to England in the subsequent Grand Slam game at Lansdowne Road, O'Gara was cornered in a forlorn section of the ground (Sunday internationals, by the way, always have a sad, sleepy feel to them - they are not right) and quizzed about the game. It was put to him that Clive Woodward thought the Irish did well enough.

O'Gara screwed his face into an expression of disdain that Corkmen alone can muster and spat, "I couldn't really care what Clive Woodward thinks."

You have to like a guy who even after experiencing an hour of utter inferiority walks away more full of fire and arrogance and anger than ever.

O'Gara is a true decision-maker in that he never questions himself and is a true gatherer of points because the only kick that matters to him is the next one. He shoots without a conscience.

But Humphreys, despite being perceived as having a comparatively fragile temperament, has enjoyed several nerveless and peerless moments of his own, landing a famous conversion against France a few years back to turn logic on its head with a famous victory for the Irish. And when he is on song, it is as if he has the very secret of the game folded up in his back pocket.

The most remarkable thing about both men is that, since their rivalry took true shape, they seem to respond admirably to one another's form. Not only are they dealing with the normal pressures that come with practising the outhalf role at a world-class level, they are also burdened with the knowledge that every squandered penalty or poor decision is being watched by a player ready to step into their place.

So far, Eddie O'Sullivan has orchestrated this delicate interchange with great care and skill. There have been moments to quibble with. Maybe O'Gara could have been introduced 10 minutes earlier in that Grand Slam against England instead of just after the deluge had begun. And maybe Humphreys, if he was to be brought in, deserved five or six minutes more against the Australians last week.

As it was, though, his introduction was just a single kick and a terribly short distance away from being heroic.

On we move to this game against France; a game played on the other side of the world which we will watch while it is dark and windy outside, bleary-eyed on our sofas. A game of massive consequence for Irish rugby, which has been promising to pioneer a trail for the past few years.

O'Gara, then, gets the nod. The kid stays in the picture. Regardless of what happens, we know we will be in a cocksure pair of hands. The intrigue comes in wondering when and if Eddie O'Sullivan springs Humphreys and then in seeing how the Ulster man can alter or improve the pattern of the game.

The one thing you can be certain of is that, if O'Gara does come off, he will absolutely hate it. And it is likely that the change will happen, if only because O'Sullivan - rightly - feels that either player is too good to leave sitting for a full game.

So for one more occasion anyway we get to see them as an entity, as our ace card with the future in their hands and at their feet. And if ever Ireland needed them at the peak of their respective games, it is now.