This, he believes, is his time to shine, and so, after a relaxed day - he says he will set his alarm to wake up in time for breakfast - Parker will take the longest walk of his life behind uncles Su'a and Rudy to the ring.
The atmosphere will be chaotic, whipped into a frenzy by legendary ring announcer Michael Buffer, and fuelled by Cardiff's notorious love of a good evening out and the knowledge that the eyes of the world will be focused on this part of the UK, at least for a short time.
The All Blacks have played in some frenzied occasions here, but nothing they have faced in Wales will compare to this - a seething mass of 78,000 people and a worldwide audience of millions.
Parker, the WBO heavyweight champion from South Auckland, who turned professional only six years ago, is confident he will beat Joshua, the WBA and IBF title holder, a man with whom he has been on a collision course for years.
It will be only the fourth time in heavyweight boxing history that two undefeated champions have fought in a unification bout; the others were Joe Frazier v Muhammad Ali in New York in 1971, Mike Tyson v Tony Tucker in Las Vegas in 1987 and Tyson v Michael Spinks in Atlantic City in 1988.
And the comforting thing for many people who have followed Parker's career since he turned professional in 2012 is that he has been conducting himself as a champion for the past three months, and in particular the past fortnight.
He has been disciplined in camp, and relaxed and professional in front of the public eye in the UK. The many fans he has made here will likely remain with him no matter the result.
The attention hasn't fazed him - in fact, he has thrived on it. Joshua, the 2012 Olympic gold medallist who has won all his 20 professional fights by stoppage, is by far Parker's greatest challenge, but the the 26-year-old is up for it.
Joshua, the biggest boxing star in the world, is motivated by the fear of defeat and as a result appears rattled.
A couple of days ago, Parker invited the Herald into his hotel room in Cardiff Bay, a room with a view of the water and city centre, including the low-slung stadium where he and Joshua will do battle.
"Is that it?" he asked. When answered in the affirmative, he said: "78,000 people. Wow, the atmosphere is going to be awesome."
Determined to enjoy every minute of the seemingly interminable fight build-up, Parker will carry that attitude into the ring.
He hasn't always been this committed to the cause. Blessed with natural talent - size, toughness, quick hands - he took it all for granted until relatively recently.
The elbow surgeries have helped. Previously, sparring sessions were halted after four or five rounds but in this camp, he has sparred 12 rounds against quality opposition without difficulty. There is something else, too - a desire to make history, after perhaps "coasting" through his previous camps.
"It wasn't me at 100 per cent," Parker told the Herald about his camps before the Razvan Cojanu and Hughie Fury fights - his two world title defences - in particular. "I'm there to fight and I want to win, but my body wasn't there properly.
"This camp, I haven't had chocolate for 10 weeks. In the last camp, I had chocolate every day. Even though I was training hard, I wasn't eating clean. Last camp, I had burgers twice a week. This camp, I haven't had a burger for 10 weeks. Last camp, I had fizzy drink here and there. This camp - nothing.
"I haven't slipped up once on anything. Having done everything right, there's no doubt there. If he beats me, he's the better man on the day ... but he won't beat me. Styles make fights and his style suits me."
He is ready. Now, two nations wait, and hope.
