For 80 minutes tomorrow afternoon good friends Vern Cotter and Joe Schmidt will be sworn rivals. There will be the normal pleasant formalities between the two respective head coaches before the game, but under the smiles and the handshakes will be a fierce rivalry with each coach hoping to succeed at the other's expense. This is war.
For a few years now the so-called European dream coaching team of Cotter and Schmidt has been bandied around in New Zealand as a potential future coaching ticket for the All Blacks, and it will be interesting to see if that scenario eventually materialises after the next World Cup in 2019.
Scotland proved to be the surprising better performing Northern Hemisphere team in the last World Cup. Only a last-minute loss to Australia prevented them being the only team this side of the equator to make it past the quarter-final stages.
Vastly improved under Cotter's short enough reign, a win against Ireland after a morale-boosting home win against Franc,e would see Scotland finishing with three wins in-a-row, something that is almost unheard of in the Scottish game over the past 20 years.
Scotland would also finish ahead of Ireland with a win in this year's Championship, so there is plenty left to play for this weekend. Ireland must be wary of Scotland's new set-piece game, especially with ex-Leinster second row Nathan Hines now plotting Scotland's attack out of touch.
The Scots possess a huge lineout, but will have to do without one of the impressive Jonny Gray, who suffered an injury against France.
In South African-born tight-head prop JP Nell, Scotland has unearthed one of the rising stars of this Six Nations, and not far behind him is another in a long line of kilted Kiwis, John Hardie.
The former Otago Highlander is perhaps the best out and out number seven in the championship to date, and his battle with the excellent Josh van der Flier would have been intriguing. Instead, Tommy O'Donnell will play the crucial part in how Ireland gains and controls the second-phase possession.
Van der Flier's work off the ball last week was immense, often driving past the ball-carrier in the clean-out and allowing Irish scrumhalf Conor Murray good quick ball.
Schmidt's coaching philosophy is one of promoting selfless players who will do the donkey work before getting the individual accolades, and the likes of Van der Flier and hard-working second row Donnacha Ryan epitomise that role perfectly.
It's pretty obvious that Ireland won't get afforded the extra space they did against a poor enough Italian side, and if Ireland are to kick for territory, then they will be well advised to keep the ball away from Scotland's last line of defence, Stuart Hogg, who nearly always beats the first line of defenders with his dancing feet and also sets up a lot of Scotland's counter-attacks.
Scotland showed a more ruthless edge last week, but have generally been a team that has found it hard to close out tight games.
Often in the past few years Scottish sides have enjoyed a wealth of territory and possession but have struggled to always make it count.
But they will have gained a lot from their victory against France, especially in regards self-belief and confidence, and they will know that while they lack real game-breakers in some key positions, if they just work hard and are patient then they do have the ability to get over the try line.
In my opinion, they still have a slight weakness where Ireland is strong - in the key areas of eight, nine and ten.
Cotter is still unsure as to who his best number eight is, having tried three players in that position this championship, although South African-born Josh Strauss has always been a serious operator for Glasgow in the Pro 12.
Captain Greg Laidlaw is a fine leader and a great goal kicker, but takes too much out of the ball. In scrum-half speak, Laidlaw is regarded as a stepper rather than quick distributor, meaning that he will always take a couple of steps before he releases the ball to his backline.
That allows defences to put greater pressure on Scotland's inside backs. Schmidt will also know from video evidence that unlike, say, the likes of Danny Care, Laidlaw is not known as a sniper around the fringes.
Most of Scotland's carries come from their second-rows who act as auxiliary back-rowers and to me this is another area that Ireland can target with quick line speed, as Scotland seem to prefer to build the phases rather than risk too many off loads.
Ireland need to learn from last week that they can in fact play in an expansive manner, it's just a matter of finding the space and taking the better option when they get the chance.
Last week, at the very start of the game, Ireland had a great chance to open Italy up out wide but the option was a box kick to the single Italian player in waiting. It was the default setting, straight from the training field. The best players and the best teams in the world play what's in front of them first, and they know that an attack pattern or a defence strategy can change in a heart beat.
Hopefully, last week's nine-try fest will give the Irish players more confidence to express themselves.
It will be tough but the Ireland players are more experienced at winning at this level than Scotland.
Expect the visitors to have plenty of self-belief and bravery, but Ireland to be a little more street-wise in key areas to let Mr Cotter get one over his old mate.