Never short of drama in recent years, Wales host Ireland desperate to end their recent losing run of seven consecutive defeats.
Last year's encounter between the two sides in Dublin was a tale of five tries, two tip-tackles of varying severity, and a 79th minute penalty from Leigh Halfpenny to set Wales on their way towards a third Grand Slam in seven years.
Go back a year earlier and the contentious 'ballgate' incident that led to a try for Mike Phillips was another incident that left Irish fans fuming. There is no love lost between these two Celtic brothers.
Focusing on Wales, Rob Howley's coaching record as the interim leader of his country reads painfully - with seven losses out of seven matches in charge. It does not however tell the full story.
In many ways their most recent loss to Australia is an example of how Wales have failed to turn narrow margins in their favour, a far cry from Halfpenny's penalty against Ireland or Scott Williams try at Twickenham last year.
Key players from the Grand Slam side who will be missing for either all or part of this year's campaign include Bradley Davies, Luke Charteris, Ryan Jones, Alun-Wyn Jones and last year's player of the championship Dan Lydiate - key personnel whose absence has left Wales worryingly short at lock.
It means that Andrew Coombs, a converted back-row from the Dragons, will make his debut against Ireland with Harlequins second-row Olly Kohn ready to come off the bench. Neither would have been given the slightest consideration a year ago, yet needs must and Wales need locks to challenge a competitive Irish line-out.
Their talented backline including George North, Alex Cuthbert and Jonathan Davies all have the potential to cut loose, but not if they are starved of possession.
As for Ireland, with France and England to come at home later in the tournament, winning in Cardiff is pivotal if they have any hope of winning a first title since 2009.
The guard is most certainly changing, exemplified by the likes of Peter O'Mahony, Craig Gilroy and a new captain in Jamie Heaslip.
November's heavy win over Argentina proved what Ireland can do when they get it right, rather than glossing over their problems as critics have suggested. The return of Leinster and potential Lions trio Rob Kearney, Sean O'Brien and Brian O'Driscoll to the national side will be a significant boost for coach Declan Kidney.
Prayers will have already been said regarding the fitness of Mike Ross but keep him fit and Ireland have as competitive a scrum as any side. It's when you take him away that the problems begin.
Ones to watch:
For Wales: The only uncapped player in the Wales starting XV, all eyes will be on Andrew Coombs when the lock runs out in Cardiff. A latecomer to Test rugby at 28, Howley has described him as "excellent in the line-out" and with a work-rate that is "second to none." With more established stars gradually set to return from injury, this is Coombs' chance to make an impression. The other key figure will be Dan Biggar. Hounded by criticism throughout his career, the Osprey is producing his best rugby and remarkably is still only 23. With Rhys Priestland sidelined, Biggar must take his chance.
For Ireland: The first new Irish captain in a Six Nations since 2003, Jamie Heaslip has a fair bit of pressure on his shoulders in trying to emulate the Irish great O'Driscoll. But, O'Driscoll cannot go on forever and Ireland need to look forward. Two victories and a loss under Heaslip's leadership in November have been enough to convince Kidney to give him the role permanently, and his enthusiasm for the role is undeniable. Surrounded by experience, it may even see Heaslip produce his best form. Elsewhere, the dual wing threat of Craig Gilroy and Simon Zebo could light up the championship and will cause Wales problems.
Head-to-head: The battle between two potential Lions. Howley has highlighted the Welsh scrum as a strength and for that to be proved right, Adam Jones will have to be superior against Cian Healy. For all his power and presence around the park, doubts linger in some circles over Healy's scrummaging ability against the best. If Healy can blunt the Welsh weapon, Ireland's chances will be strengthened.
2012: Wales won 23-21 in Dublin
2011: Wales won 22-10 in Wellington
2011: Wales won 19-13 in Cardiff
2010: Ireland won 27-12 in Dublin
2009:Ireland won 17-15 in Cardiff
2008: Wales won 16-12 in Dublin
2007: Ireland won 19-9 in Cardiff
2006: Ireland won 31-5 in Dublin
2005: Wales won 32-20 in Cardiff
2004: Ireland won 36-15 in Dublin
2003: Ireland won 35-12 in Dublin
Prediction: The problem with seven losses on the bounce is that it breeds no momentum and no confidence. Wales are a better team than their record suggests, but the question is whether they believe it. Easing the line-out worries with Aaron Shingler deprives them of Justin Tipuric's ability at the breakdown, meaning they must benefit from the scrum. Ireland hold more cards and have Sexton at the helm. A narrow margin as ever, but an Irish win in Cardiff. Ireland by 6.
Wales: 15 Leigh Halfpenny, 14 Alex Cuthbert, 13 Jonathan Davies, 12 Jamie Roberts, 11 George North, 10 Dan Biggar, 9 Mike Phillips, 8 Toby Faletau, 7 Sam Warburton, 6 Aaron Shingler, 5 Ian Evans, 4 Andrew Coombs, 3 Adam Jones, 2 Matthew Rees, 1 Gethin Jenkins.
Replacements: 16 Ken Owens, 17 Paul James, 18 Craig Mitchell, 19 Olly Kohn, 20 Justin Tipuric, 21 Lloyd Williams, 22 James Hook, 23 Scott Williams.
Ireland: 15 Rob Kearney, 14 Craig Gilroy, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 Simon Zebo, 10 Jonathan Sexton, 9 Conor Murray, 8 Jamie Heaslip, 7 Sean O'Brien, 6 Peter O'Mahony, 5 Mike McCarthy, 4 Donnacha Ryan, 3 Mike Ross, 2 Rory Best, 1 Cian Healy.
Replacements: 16 Sean Cronin, 17 Dave Kilcoyne, 18 Declan Fitzpatrick, 19 Donncha O'Callaghan, 20 Chris Henry, 21 Eoin Reddan, 22 Ronan O'Gara, 23 Keith Earls.
Date: Saturday, 2 February
Venue: Millennium Stadium
Kick-off: 13:30 GMT
Referee: Romain Poite (France)
Assistant referees: Jaco Peyper (South Africa), Pascal Gauzere (France)
Television match official: Graham Hughes (England)
by Ben Coles