Get ready for the Six Nations buzzword around this time of the year – momentum. One game at a time and all that; but winning the opening match is even more important. Win that, and a team has momentum. Lose it, and they are playing catch-up.

In the context of the Championship, few teams have underlined this truism more than the Irish and the Welsh. Throughout the Naughty Nineties in the Five Nations, Ireland lost their opening game for 10 years in a row, and only once recovered to win even two of their remaining four games, thereby finishing fourth or fifth in every one of the last 10 Five Nations campaigns.

The pattern changed at the turn of the Millennium for despite losing 50-18 at Twickenham (remarkably, Ireland did recover to win three of their remaining four games to finish third). Ireland have won 10 of their last 12 openers, the exceptions being the 35-17 defeat in Paris in 2004, after which Ireland won four successive matches to finish second and win the Triple Crown, and last year’s 23-21 defeat at home to Wales.

It assuredly helped that Italy provided the opposition in six of those 10 opening weekend wins, but the only time Ireland finished in the bottom half of the table was in 2008, Eddie O’Sullivan’s final campaign in charge.

But the importance of an opening-day win is emphasised even more by the Welsh. On the five occasions they began with a victory, they went on to complete Grand Slams, while in the eight years they lost first time out, they finished in the bottom half.

Maybe it says something about the volatility of the Welsh rugby temperament. Maybe it also says something about a brittle Celtic temperament, although the importance of gaining momentum on the opening weekend applies to the tournament as a whole.

Opening match

Only once since 1996 have the ultimate champions won the title after losing their opening match, namely in 2006 when France recovered from a 20-16 defeat on the opening Sunday to win their ensuing four matches and finish above Ireland on points difference.

Come Sunday tea-time therefore, we can most probably draw a line through the table. “And then there were three.”

This feeling is strengthened by the likelihood that England will beat Scotland at home and France will win in Rome, leaving the Ireland-Wales game as something akin to a title eliminator, which is exactly how it looks.

The pressure is accentuated by the background to the game. For Wales, an eighth successive defeat (and sixth under interim head coach Rob Howley) would further undermine a coaching ticket destabilised by Warren Gatland first being incapacitated on their summer tour to Australia and subsequently obtained by the Lions, and leave them facing three successive away games. But a win would turn their mindset around and remind them of last season’s Grand Slam glory.

For Ireland, a fourth successive defeat to the Welsh would suddenly give the impending visits of England a week later and bugbears France in round four an even more daunting look. It would devalue much of the goodwill generated by the November campaign which came in the absence of their last three captains plus Rob Kearney, Seán O’Brien and Stephen Ferris. It would also undermine that new leadership dynamic and, if only slightly, the captaincy call.

Extending their reign

For Declan Kidney, Les Kiss and Gert Smal, a strong campaign would enhance their prospects of extending their reign to the 2015 World Cup. For that to happen, Ireland needs to win at least three or four games while performing consistently, ie no more Terrible Twickenhams or Horror Hamiltons , not least as they overshadowed Ireland’s best performance and result in Paris for 12 years and nearly beating the All Blacks in Christchurch.

If the evidence is things have become stale after five championship games under this coaching ticket then the clamour for change is liable to be deafening.

But were the performances to mirror the style and ambition of the win over Argentina, all the better, and if it were to come with a real tilt at a second Six Nations title, it would brook no argument.

Kidney and co would have shown the class of 2009 has been largely rebuilt, and is moving forward. This would be healthier than finishing this Six Nations on a low ebb and having to start all over again, all the more so without an obvious successor bar the usual international suspects, unless Joe Schmidt was prepared to take on the job and stay beyond next season.

By signing for one more year with Leinster, it would appear his future depends more on his family than anything else, and one ventures it would take a remarkable offer to lure Conor O’Shea away from Harlequins.

Sticking with coaching regimes when not a popular decision can reap dividends too. For example, the coaching tickets headed by Clive Woodward and Graham Henry, after much criticised World Cups in 1999 and 2007, were both rewarded with the Webb Ellis Trophy four years later. But it all hinges on the 2013 Six Nations, which in turn hinges on the opener. So, not much pressure in the Millennium Stadium then come 1.30pm next Saturday. Not much pressure at all.