As a key figure in the Irish attack, the All Blacks have made it clear they will target him.
No surprise there, every international playmaker is considered fair game to opposition defences – especially by fired-up loose forwards – but Steve Hansen's men will figure that should they shut down the now 34-year-old who was last year named the world player of the year, they will go a long way towards winning the match.
"You want to try to put any playmaker under pressure but it's easier said than done," All Blacks flanker Matt Todd said. "That's certainly our plan, we want to take away his time and take away his space and make it as hard a night as we can for him because he is such a key player for them."
The Irish attack has been criticised, perhaps unfairly, as being one-dimensional and solely reliant on either Sexton or halfback Conor Murray. But, while they have a world-class outside back trio, which includes fullback Jordan Larmour and wing Jacob Stockdale, there is an element of truth to it.
Much of their try-scoring opportunities come directly from either the hands or feet of Sexton or Murray. Stymie either of those two or both and the All Blacks are likely to have a happier night in what is a highly-anticipated quarter-final.
"Every team has their strengths and weaknesses," assistant coach Ian Foster said. "We know Johnny Sexton is important to their team. We know that a lot of the ball does go through his hands. That's clear and obvious, I think everyone knows that.
"But they're a smart rugby team and they've proven that. People can say what they like about their attacking style and defensive style but they're efficient and do it well. That's what makes this exciting for us because we're playing a team that knows how to play and what greater challenge could you have?"
Foster didn't want to delve into the three-match ban for midfielder Bundee Aki other than to say it was "consistent" and that the Irish had some other "great midfielders".
And while the All Blacks will be preparing for Murray's box kicks, especially inexperienced wings Sevu Reece and George Bridge, they weren't focusing entirely on it.
"Catch them," Foster said of the key to defusing Murray's bombs. "They've got some weapons in their arsenal. It's like any other game, really. We'll work on our high ball catches like any team that would kick it there. It's something that's worked well for them and we've just got to make sure we're really proficient in that area."
It may however, come down to a clash of styles; the All Blacks' commitment to a high-tempo running game which Japan used to such great success against the Irish in their 19-12 upset here, against a forward-oriented bash and crash no-mistakes style of the Irish.
Japan, the All Blacks, Scotland, the Wallabies and to some extent the Springboks have had some success with their running game here, but is the swing back to a conservative style coming? And do the All Blacks have the courage to take high-risks in a sudden death game?
"It's a really good question because it's where you go when you're under pressure isn't it?" Foster said of the first question. "And that's the exciting part of this part of the tournament."
The answer to the second one appears to be yes.
"We still want to be confident to play against the pictures that we see. We trust the guys to execute and make decisions but sometimes pressure can do funny things to people. And you can eliminate all the risk from your game.
"We've got a do or die game against Ireland," continued Foster, who added that the All Blacks were more than ready for it.
"They're a high retention team, so they like to hold the ball and they'll use the kick when they feel they're under pressure or when they sense weakness. We're not expecting a barrage of kicking, we're expecting them to want to hold the ball for a lot of rucks and tackles. That's their style."