There's rain in the air and there's optimism in the air, and one's as disconcerting as the other.

Certainly, the amount of confidence on Ireland's behalf from pundits (even the normal prophets of gloom) and punters alike is almost unnerving, while the forecast rains, even if they abate by the time of kick-off, are likely to dilute hopes of a free-flowing feast.

Eddie O'Sullivan reported the pitch to be firm underfoot at yesterday's final run-out on Lansdowne Road.

But heavy rain was forecast overnight and again this morning, and memories are too fresh of the pitch's poor drainage system last November to dispel fears that the drying afternoon wind will merely worsen playing conditions.

In such a climate, as he proved in the, eh, autumnal matches against Australia and Argentina, Girvan Dempsey is as safe as houses.

Alas, a reaction to his ongoing groin problems after Thursday's full-scale session has ruled him out. So, Geordan Murphy reverts to full back, with John Kelly again on the right wing and Rob Henderson on the bench.

As this means the same backline en bloc as played last time out in Rome, it shouldn't, as O'Sullivan conceded yesterday, discommode Ireland unduly.

The Irish backs have grabbed the glory, dispersing the eight tries scored amongst half a dozen of them, but the real heroes have been the pack.

All bar Murphy's stealthily manufactured try off turnover ball on the Irish 22 against the Scots were fashioned by the pummelling or continuity of the foot soldiers.

The watching French have taken note. They are not coming over here to chuck it around in time-honoured fashion.

As O'Sullivan recognises, they are coming over to try and do a number on the Irish backs, and will target the setpieces to nullify the Irish backs at source.

The French scrum - a badge of honour to them - has felt emasculated by refereeing so far and, with Reggie Corrigan sidelined, will go for the jugular.

"The big thing about the French scrum is that all eight of them push," says Shane Byrne. "You might get some packs where one or two of the back-rowers will be looking towards the next play, but not the French. They all contribute."

Byrne and Corrigan have effectively attacked opposing tight-heads, and without his sidekick the Irish scrum probably won't be such a weapon today.

Byrne will be obliged to take a more protective role perhaps, but is utterly confident that "Marcus will be fine". The pressure will come from Jean-Jacques Crenca.

A soft pitch is liable to make the scrums more important, but if John Hayes scrums straight (which he always does) and low, Ireland should survive.

In this, and much else, Andre Watson is a key man. One of the world's best referees, Ireland haven't had him since their last home defeat to New Zealand over a year ago.

There'll be a good contest at the breakdown, for he is particularly hot on players releasing when going to ground, but also on opposing players staying on their feet.

Though French lock Olivier Brouzet is essentially a lifter these days, the French will still loft two or three jumpers in the air, with Olivier Magne supplementing Imanol Harinordoquy and Pelous - peerless at the front.

Gary Longwell, particularly, will have his hands full, but the impressive aspect of the Irish line-out this season - aside from Byrne's accuracy, the cohesion of lifters/jumpers and the sheer excellence of Malcolm O'Kelly - has been its movement.

With two well-drilled defences who've only conceded one try apiece in over 320 minutes of rugby, openings will be at a premium. And "linebusters" will be invaluable.

Shackling the dangerous, but hitherto subdued, Magne is imperative to Ireland's chances, but the suspicion watching the famed French backrow this season is they need a dominant front five and space out wide to operate in.

Victor Costello is again potentially the key man. He is a more natural linebuster than the French backrowers and no one has done more to give the gifted runners out wide front-foot ball to operate off.

France will also be an infinitely more disciplined and mentally tougher team than the one of, say, even two years ago. But again they will be without the hugely influential Fabien Galthie, and there has to be doubts about such inexperienced French halves.

If Francois Gelez had Costello and Kevin Maggs stampeding at him in his sleep, then the reality probably won't surprise him.

The Irish halves have been around the block a good deal more. It'll be a special day for David Humphreys when he leads the team out on his 50th cap, though Brian O'Driscoll quipped yesterday, "over my dead body".

Ireland are marginal, four-point favourites, which shows how genuinely it hinges on the vagaries of the day.

However, optimism on behalf of Ireland is well-founded - seven successive home wins and 10 wins out of 11 dating back to November 2000 has a tendency to do that.

It's the winning mentality that counts, witness the high win-loss percentages of each, best epitomised by O'Driscoll's record of 17 wins from 17 games this season, including five as captain of Ireland.

One cannot recall such a well-rounded Irish team in the last 18 years, nor one that will be as well-prepared.

And with home advantage and the momentum of an unprecedented eight-match winning streak, they have a better than 50-50 chance.

If you had to put your mortgage on either of them, it would be Ireland.

Not that you'd be remotely inclined to.

It's liable to be edge-of-the-seat stuff anyway.