A defining day on New Zealand's North Island is likely to be shaped by just two men. Beauden Barrett and Owen Farrell, fly-halves in black and red respectively, will ultimately influence the first Test scoreboard more than any of their team-mates as they make best use of the possession that comes their way.
All Blacks selector Grant Fox, the fly-half who kicked New Zealand to victory over the Lions in 1993, calls it "a battle of wills", a contest in which neither man is likely to blink first. Farrell, according to Fox, has "no weaknesses"; Barrett, meanwhile, is the fastest No 10 in the modern era. In a match full of intriguing sub-plots, it is surely the most significant.
As Auckland filled to bursting with Lions fans, swarming along every street and thoroughfare, Farrell himself declared that it was important "to play the game and not the occasion".
"You can't be thinking about what other people are thinking about, getting excited about external things," he reflected. "It has got to be about the team and what we need to do to win."
Farrell has recovered from the thigh strain that caused him to miss last Saturday's match against the Maori All Blacks in Roturua. The 25-year-old has grown in stature with each passing season since he understudied Jonathan Sexton on the 2013 Lions tour to Australia. If the Lions are to pull off an upset then the half-back axis with Conor Murray will be pivotal.
Fox and the All Black management are well aware just how influential Farrell is. "Owen just does everything well and we don't see any weaknesses there at all," he said. "He is a very smart player, runs good lines and is very good at putting people into space around him. He is courageous down that channel, too, and that is not always a trait of No 10s.
"That comes maybe from playing out one at inside centre and having to deal with that. Playing at No 12 [for England outside George Ford] has probably given him greater awareness of what the guys outside him need and what they're looking for. That certainly would have helped his development. Owen is a hell of a good player."
But so, too, is the man opposite him, the world player of the year, sharp-eyed and spring-heeled. Fox has never seen the like in terms of the pace offered by Barrett.
"In the modern era I don't think I've seen anyone as quick as him," said Fox. "Off the bench he used to cover two positions [full-back and fly-half] for us, which gave us flexibility. He could come on when people were tired and kill defences. But Beauden wanted more than that. He wanted to be a starter, so he went away and worked hard. If we are being brutally honest, we probably saw him as a 15 who could play 10, but now he has proved us wrong. He is a 10 who can play 15 - and last year he had a breakout year in the 10 jersey. He has found it tougher against some rush defences - and we know that is what the Lions will bring."
And the All Blacks will offer plenty of options themselves, all over the field, from the strength of their own forward pack to what Fox describes as the "triple threat" kicking style of Barrett, who can kick conventionally high, or grubber through as a means of countering the Lions' rush defence or utilising what has become known as the kick-pass, the little dink right or left into the hands of the wing. Allied to that is his short passing game to tee up Sonny Bill Williams, whose offloading is such a potent part of the attack.
"It is pretty clear how good a player Beauden is," said Farrell. "He is one of New Zealand's main threats but there other things too. You don't want to go high on Sonny Bill, just tackle him, and there are adjusting defenders around him who are prepared for the offload."
Farrell has been tutored in his defensive duties by dad Andy, the father-son, coach-player relationship renewed for the first time since the 2015 Rugby World Cup. There has been no special reunion. "I've not being talking to him too much as my dad, no," said Owen. "Not at all on this tour, in fact. There are lots of little conversations, though, that go on all the time to make sure everything is covered. I didn't know when to say anything to him on Father's Day as I didn't want to say it in front of anyone. Everybody got some video messages. They didn't think to ask me so I was a bit gutted about that."
The touchy-feel stuff is not the Farrell way, on or off the field, as Saturday will surely show. The Barrett-Farrell head-to-head will be quite some game within the game.