Veteran star can get the better of Russell and drive Schmidt’s men on to victory in the unforgiving Yokohama conditions
We begin with a question. The rain is falling, the wind is blowing hard and the forwards are going hell for leather. The tackles are flying, the ref is letting things go and the carries are hard and you look up to the man whose job it is to rise above and control the game.
Who would you rather see: Johnny Sexton or Finn Russell?
In this world of dominant collisions, the quarterback remains the king.
In Sexton, Ireland have a man who can mix fire and brimstone with the consummate decision-making calm. He may be 34, but he remains the World Rugby Player of the Year.
Russell is a class act with the ability to blow a match wide open, but he is no Sexton when it comes to running a team. And that is what will be needed when it comes to the white heat of the battle of Yokohama on Sunday.
These two teams are evenly matched and the suggestion is that the Scots don't think much of the world's No 1 team. Privately, they reckon they're better rugby players and often leave the field frustrated to have lost to a collection of individuals who find it easier to find their voice as a choir.
Scotland have the propensity to play the more exciting, aesthetically pleasing rugby and their coach Gregor Townsend talks a good game. They want to be the fastest rugby team on the planet, but that's no good when you can't win clutch games.
There have been exceptions. Glasgow hammered Munster in the PRO14 final when Townsend was coach in 2014, while the Scots beat Ireland on the first day of the 2017 Six Nations.
Joe Schmidt's complaints about bus delays rubbed the locals up the wrong way and the sense that there's no love lost between the teams has run through a number of their games, with Sexton often the target of Scottish ire and late, thundering tackles.
There is a Scottish conspiracy theory that Irish teams have gone after Stuart Hogg and he has been forced off injured in the last two big games he played against Irish sides.
It doesn't help their persecution complex that Peter O'Mahony escaped sanction for connecting to the flying full-back's head with his elbow, while Rob Kearney only saw yellow for upending him in the PRO14 final.
If indeed they are targeting an individual, and it's something they'd deny, it's interesting they've chosen the explosive full-back rather than the No 10.
Perhaps there's a sense that Ireland can manage Russell into positions where he's forced to make decisions and feel they have the capacity to upset him. Maybe they reckon they can get to him.
Like all out-halves, Sexton and Russell depend on the quality of ball they get from their forwards.
Scotland have a strong lineout and a decent scrum, but Ireland will back their pack to be better.
If they can secure possession out of touch, then they'll turn to a collection of forwards laced with ball-carrying threat and ground and pound their way to victory.
Before his side destroyed Ireland in the Six Nations, England's Ben Youngs said you have to beat Joe Schmidt's side in the air and on the ground.
Given their back-three struggles, they'll try to keep this contest on terra firma and run over the Scots. But when they run aground in contact, they'll have kicking options aplenty.
Leaving aside the injured Dan Leavy, Schmidt has picked his first choice No's 1-10; a strong centre pairing and a prolific winger in Jacob Stockdale. Jordan Larmour and Andrew Conway are accommodated in the absence of Rob Kearney and Keith Earls and will know Scotland will test their positional sense.
Likewise, Murray and Sexton will look to find space in the Scottish backfield and pull their talented back three around the park. Garry Ringrose is another whose kicking game can open up opponents.
In the Six Nations, we saw a shift towards an increase in tactical kicking and Ireland fans can expect to see the team look to probe.
"We have certain things we're looking to do and some of that stuff you will have seen over the last while," skills and kicking coach, Richie Murphy, said. "And, again, it is strategy because you're reacting on what you are given because it mightn't be an exact plan going into a game saying what you're going to do.
"It's based on what you're going to do, it's based on what's happening around with the movement of the back-field and the opportunities that are being presented is what we're reacting to. We need to paint different pictures probably for defensive teams and getting into aerial contests has been difficult for the last while.
"So, trying to kick to places where there's less numbers gives us better access to get into the challenge."
If they get the chance, the Irish back-three is laced with danger, but it looks like a game that will be won up front and by the half-backs.
Those two will be key to everything Ireland put together this month. In the final warm-up game against Wales they looked back to the level they had attained in 2018.
Once battle commences, both teams will look for leaders.
In Sexton, Ireland have an unrivalled operator ready to rise to the occasion. He is the answer every day of the week.
Rugby World Cup 2019
With a day to be spent away from their Minato City base and the training paddock yesterday, the Scottish squad took in day 12 of the Sumo Grand Championship at the Ryogoku Kokugikan.