The captain, Sam Warburton, is predicting a "proper epic Test match" as New Zealand seek to bounce back from their 24-21 defeat in Wellington.
In this third test, Sexton will play his sixth Lions test in a row, five of them as the starting out-half.
That will change on Saturday when (barring a late illness or injury) the Lions will throw the same 23 at New Zealand that beat the All Blacks in Wellington.
The Lions' three playmakers - Conor Murray, Johnny Sexton and Owen Farrell - initially reacted poorly to Williams' dismissal. Anthony Watson 13. Jonathan Davies 12. Reps: K Owens, J McGrath, K Sinckler, C Lawes, CJ Stander, R Webb, B Te'o, J Nowell. I don't think about the future.
"We'll get the best out of everyone if we do enjoy it. Work sometimes becomes an obsession and that's not good".
"We've got to make sure that physically we are on it, mentally we are on it, we know our stuff and we can go into the game with clear heads and really attack it". We've played a good brand of rugby and people have been surprised and nearly reluctant to give us credit for that.
"I have no doubt. the players will start thinking about it later on but there's no point in getting emotionally too involved". You have those moments in your life and you don't want those moments to pass you by. "You've got to embrace that".
"There's a group of players there who are incredibly competitive and realise this is a massive opportunity to win a series in New Zealand", he said.
DAVID GRAY REUTERS
Liam Williams plays after missing training in Queenstown on Wednesday
Elsewhere, Ngani Laumape lines up at centre instead of the suspended Sonny Bill Williams, wing Julian Savea is recalled for Rieko Ioane and Israel Dagg switches from full-back to right-wing with Waisake Naholo dropping out.
Having officiated in the Lions' final midweek game against the Hurricanes, Frenchman referee Romain Poite will run the rule over the third and final Test. Laumape can set the All Blacks up in midfield.
Williams has really grown into this Lions Tour and is clearly a prospect that will excite the Saracens fans heading into the new season.
Jordie Barrett comes into the side for his first test start and speaking to Joe Molloy, Thornley said: "Yeah, that had been flagged but it's still a little bit surprising".
While Warburton says the squad have embraced Lions history, he added they have to rein it in on Saturday in order to be successful.
The Lions though just seem to lack spark off of the bench in certain areas and a fresh Vunipola, to pair with a fresh Kyle Sinkler on the 55-minute mark, would be tough for the All Blacks to handle.
Perhaps more telling than praise from northern hemisphere pundits was criticism in New Zealand media about Itoje's "cynical" repeated offside infringements as the match hung in the balance. The pair used to wear out the parallel trails on the Rugby Park pitch in Christchurch so close and so hard-working were they, but, on the eve of Read's biggest test, McCaw will keep a bit of distance.
The All Blacks have won the last two World Cup finals and those were occasions which had their own flawless storm of pressure and expectation.