So this is it, the defining match of the RBS Six Nations Championship, for all sorts of reasons one of the most eagerly awaited games of the year and an international that will go a long way to determining the destiny of the title. If Wales can win today in Dublin for the first time since 2000, only a mixed-up France team will stand in their way of sealing a grand slam in Cardiff. If Ireland can prick the Welsh balloon, the championship is not beyond them. Throw in the Eddie O'Sullivan-Warren Gatland sub-plot and the prospect this afternoon is mouth-watering and fascinating.

This is the ultimate challenge for Wales, a real examination of their credentials and an opportunity to gauge how much substance there is to their revival. So, too, is it Ireland's. Although Gatland, the Wales coach who was replaced by O'Sullivan at Ireland in 2001, poured scorn yesterday on Rory Best's assertion that Wales had not been tested thus far, the Ireland hooker is correct. England imploded, a dreadfully one-dimensional Scotland were only belatedly put away, while Italy capitulated.

Dublin has proved to be a graveyard for Welsh hopes in recent seasons. In 2006, when Gavin Henson, in his own words, felt like committing suicide after a wretched display as a replacement fly half, the scoreline was 31-5 in Ireland's favour. Most of that squad of 22 are on duty today.

It has not gone unnoticed. “I know the players have been really hurt in the past by the poor performances they've had in Ireland and the wounds are pretty deep in terms of those performances,” Gatland said. “So these guys really want to give a good account of themselves.”

While there is nothing to suggest that the margin will be as emphatic, it is difficult to look beyond an Ireland win by ten points. They have too much knowhow, too much experience and are too streetwise.

O'Sullivan points to Ireland's scrum as the most improved area of their game in this championship. Rather than a mere holding operation, it is now a weapon of attack.

“It has given us a great platform,” the Ireland coach said. “We have that extra balance. The challenge for us is not to let them settle, to manage the pace of the game and to enforce our game plan on them rather than let them enforce their [game plan] on us.”

If Ireland can get on to the front foot, there is no one better than Ronan O'Gara at controlling a match, especially in the windy conditions that are forecast at Croke Park, a venue that Wales saw for the first time yesterday. Put the squeeze on and Wales's “run and gun” game, as described by O'Sullivan, will be neutered.

Shaun Edwards, the Wales defence coach, has been drumming home that message; in essence, “stop O'Gara” has been their mantra this week. Edwards witnessed how London Wasps, where he is head coach, were skewered by a kicking masterclass from the fly half in the Heineken Cup match against Munster in January.

The changes necessitated to the Ireland back three by the absence of Girvan Dempsey and Geordan Murphy - the first time since 2000 that neither has featured in an Ireland team - have also lent the Irish another significant attacking option. Shane Horgan, at 6ft 4in, and Tommy Bowe, who is not much shorter, are both taller than Mark Jones and tower over the 5ft 8in Shane Williams. O'Gara will use judiciously the cross-field kick.

A clever kicking game is the one of the most effective methods of overcoming the blitz defence system adopted by Wales. In O'Gara, Ireland have a player whose control of a rugby ball is remarkable. Gatland's “homecoming” could have an unhappy ending.

How they line up

Ireland: R Kearney (Leinster); S Horgan (Leinster), B O'Driscoll (Leinster, capt), A Trimble (Ulster), T Bowe (Ulster); R O'Gara (Munster), E Reddan (Wasps); M Horan (Munster), R Best (Ulster), J Hayes (Munster), D O'Callaghan (Munster), P O'Connell (Munster), D Leamy (Munster), D Wallace (Munster), J Heaslip (Leinster).

Replacements: B Jackman (Leinster), T Buckley (Munster), M O'Driscoll (Munster), S Easterby (Scarlets), P Stringer (Munster), P Wallace (Ulster), L Fitzgerald (Leinster).

Wales: L Byrne (Ospreys); M Jones (Scarlets), T Shanklin (Blues), G Henson (Ospreys), S Williams (Ospreys); S Jones (Scarlets), M Phillips (Ospreys); G Jenkins (Blues), H Bennett (Ospreys), A Jones (Ospreys), I Gough (Ospreys), AW Jones (Ospreys), J Thomas (Ospreys), M Williams (Blues), R Jones (Ospreys, capt).

Replacements: M Rees (Scarlets), D Jones (Ospreys), I Evans (Ospreys), G Delve (Gloucester), D Peel (Scarlets), J Hook (Ospreys), S Parker (Ospreys).

Referee: Wayne Barnes (England).