With Ireland needing a win to set up a potential Six Nations title decider with England in Dublin and Wales smarting from defeat to Scotland at BT Murrayfield, Friday’s clash in Cardiff is colossal.
The way in which Joe Schmidt’s side responded to defeat in Edinburgh first against Italy and then France suggests all is rosy, but here we assess who has been pushing their own case for inclusion at Principality Stadium and which players could make a pivotal difference.
Does Jack Conan deserve a shot in Green?
Jack Conan has been immense for Leinster of late. His two-try performance in the 54-22 victory over Newport Gwent Dragons in Round 16 was one of the most complete performance by any forward in the Pro12 this year.
The No.8 made 123 metres, he beat eight defenders and his support play was superb, backing up a string of superb performances – including a hat-trick against Montpellier in the European Rugby Champions Cup, while he was outstanding in Leinster’s stunning 45-9 win over Scarlets.
He has been a huge factor in Leinster’s ascent to the Pro12 summit during the international window, playing a talismanic role as Leo Cullen’s troops have racked up 248 points and conceded just 61 since the Six Nations began.

The only problem is that back row is Ireland’s most competitive position – in fact, it is arguably the most hotly-contested of any position in world rugby.
With Sean O’Brien, CJ Stander, Josh van der Flier, Peter O’Mahony and Jamie Heaslip, as well as Conan and Dan Leavy, embarrassment of riches scarcely covers Joe Schmidt’s selection conundrum.
The 24-year-old Conan would almost certainly have added to his single cap in any other era, but will he be able to break into Schmidt’s winning back row?
Is Peter O’Mahony the answer?
Before Munster captain Peter O’Mahony was injured in the 2015 Rugby World Cup, it was hard to imagine an Irish back row without him.
He had quickly made himself indispensable since making his debut against Italy during the 2012 Six Nations, but fast forward 18 months and the emergence of CJ Stander has put a question over his place in the team.

Stander’s relentless carrying has become a big feature of Ireland’s game, but in O’Mahony Schmidt can call upon an extra lineout option, a proven leader, a ruthless defender and an expert in the unseen work that makes all great sides tick.
In defeat to Scotland during round one, the Irish lineout was not at its best, and though it functioned well against both Italy and France, Schmidt may want to bring in O’Mahony to ensure a steady supply of set-piece ball against the Welsh.
O’Mahony could be the perfect antidote to Wales’ twin opensides Sam Warburton and Justin Tipuric if returned to the starting XV, but with either O’Brien or Stander having to make way, is it worth it?
Has Joey Carbery done enough for a bench spot?
Jonathan Sexton’s masterclass on his return to the Ireland No.10 jersey against France means there is little doubt he will start if fully fit.
His level of control and organisation are a cut above, while his 11-point haul was an exhibition of how to accumulate points in a Test match.
Paddy Jackson rose from the bench to knock over three points of his own, while he performed well both in defeat to Scotland and victory over the Italians.

But Joey Carbery’s return to Leinster colours has been nothing short of spectacular – playing both at full-back and fly-half, he has scored five tries in four games and is now tied with Tommy Seymour as the Pro12’s leading try-scorer this season.
Two months out with ankle ligament damage has done nothing to dim the ludicrous acceleration Carbery possesses and he looks more and more assured every time he takes the field.
Though it may seem bold to throw Carbery into a game with as much riding on it as Friday night in Cardiff, the Clontarf man has risen to every occasion that he has been presented with.
Two tries on his Leinster Pro12 debut and at 21, already a winner against the All Blacks, he could be a genuine gamebreaker for Ireland from the bench while also offering plenty of versatility as a replacement.