The simple answer: the series. If the All Blacks follow up last weekend's comprehensive victory at Eden Park with another win at Forsyth Barr Stadium, they will take an unassailable 2-0 lead ahead of the third test at Sky Stadium.
The more detailed answer: two sides whomay meet in the quarter-finals of next year's World Cup will be wanting to make statements with their performance; two coaches - one whose team have disappointed on this tour, the other whose team thrived after he had been stuck in the sickbay - have different points to prove; plenty of players on either side will be wanting to cement themselves in the first XV; and the All Blacks have a couple of debutants on the bench undoubtedly determined to achieve a career goal.
Coach Ian Foster and reserve halfback Folau Fakatava. Photo / Getty
Jaco Peyper of South Africa, who has overseen 15 All Blacks wins and a draw in his 16 tests in charge of the team.
He had the whistle during the 2016 clash between the two sides in Dublin, won 21-9 by the All Blacks. Though one Irish writer wasn't happy - 'Peyper failed in his duty of care to the players'.
What history says:
Here's one for numerologists. Ireland have played twice against the All Blacks in Dunedin - In 1992 (lost 24-21) and 10 years later in 2002 (lost 15-6). And now it's 20 years later from that test. Expect another visit in 2052.
In 1992 Ireland came into the first test having beaten South Canterbury, Bay of Plenty and Poverty Bay-East Coast but lost to Canterbury and Auckland.
"They were obviously not a great team," says Men in Black aka the New Zealand rugby bible.
"One of the most disturbing features of their games was the players' apparent lack of fitness and in all but one game the tourists required replacements". Ouch. We were still three years away from rugby turning pro.
Irish scored two quick tries and after an All Blacks comeback retook the lead in the second half before Frank Bunce secured a 'lucky' win.
In the 2002 meeting at Carisbrook, 13 of the All Blacks starters were from the Crusaders with Tana Umaga and Doug Howlett the odd ones out (the next week it would be 14). Robbie Deans called the game 'ugly' as both sides struggled to convert kicks with Andrew Mehrtens later labelling the yellow Adidas match ball a pig. A frozen Dunedin crowd booed the All Blacks off the field.
Andrew Mehrtens wasn't a fan of this ball. Photo / Getty
"Foster could have injected Will Jordan and David Havili, among others, into his side this week but he has instead favoured selection continuity to back those who emphatically did the job in the 42-19 Eden Park victory.
"Foster noted he wanted to give Akira Ioane (foot), Havili and Nepo Laulala (both neck) another week to progress lingering niggles but also made it clear last week's starters earned another crack."
"Who honestly, after the final whistle blew in Auckland last week, wasn't immediately looking forward to the next clash, knowing that the second test of a three-test series is always the one where the tension and intrigue are at their greatest.
"Now that both sides have learned something about each other and the series could be won in Dunedin, the pressure points have changed."
Two 100 per cent records on the line:
Both the All Blacks and Ireland have perfect records under the roof in Dunedin. The All Blacks have won seven straight while Ireland won their 2011 Rugby World Cup encounter against Italy 36-6.
The South Island fortress:
One more stat. The All Blacks haven't lost in the South Island since 2009 - a 27-22 defeat to France. Since then they have won 17 straight with nine in Dunedin, six in Christchurch and one in Nelson.
It's been a while since the All Blacks lost in the South Island. Photo / Getty
The teams:
All Blacks Jordie Barrett, Sevu Reece, Rieko Ioane, Quinn Tupaea, Leicester Fainga'anuku, Beauden Barrett, Aaron Smith; Ardie Savea, Sam Cane (c), Dalton Papalii, Scott Barrett, Brodie Retallick, Ofa Tu'ungafasi, Codie Taylor, George Bower.
Reserves: Will Jordan, Richie Mo'unga, Folau Fakatava, Pita Gus Sowakula, Patrick Tuipulotu, Angus Ta'avao, Aidan Ross, Samisoni Taukei'aho.
Ireland Hugo Keenan, Mack Hansen, Garry Ringrose, Robbie Henshaw, James Lowe, Johnny Sexton (c), Jamison Gibson-Park; Caelan Doris, Josh van der Flier, Peter O'Mahony, James Ryan, Tadhg Beirne, Tadhg Furlong, Dan Sheehan, Andrew Porter.
Reserves: Bundee Aki, Joey Carbery, Conor Murray, Jack Conan, Kieran Treadwell, Finlay Bealham, Cian Healy, Rob Herring.
