Joshua’s IBF and WBA world titles will be on the line, as will Parker’s WBO belt, in the first heavyweight unification bout held on British soil.
Some 78,000 fans are expected at the Principality Stadium on fight night – a new level of scrutiny for Parker.
“If he loses composure in the ring, I will be able to tell,” said Joshua, 28.
“Even though it’s a phenomenal atmosphere there is one ring, one referee. If I’m in any arena, you just have to simplify the madness and the chaos,” Joshua told BBC Radio 5 live Breakfast.
In the build-up, much has been made of Joshua’s career-high weight of 18st 2lbs in defeating Carlos Takam last time out. But in front of around 3,000 fans at Cardiff’s Motorpoint Arena he scaled 17st 4 lbs – his lowest mark since 2014 – and said the weight cut should make him “sharper”.
Parker too seemingly opted for improved speed in the ring, coming in at 16st 12 lbs, a drop of nine pounds.
Promoter Eddie Hearn this week told the BBC about a letter he received asking for a character reference when Joshua was in legal trouble in 2011 after being charged for the intent to supply cannabis.
Hearn said he did not know Joshua at the time and refused the request. But he recalled that months later he was at Sheffield’s English Institute of Sport and heard a noise “like something being taken off its hinges” – it was Joshua hitting a heavy bag.
Hearn went on to promote the London 2012 gold medallist.
On Saturday, Joshua will earn an estimated £15 million and sell out a third stadium event in 11 months, taking the total of sold seats to a quarter of a million.
“This has never happened in British boxing before,” Hearn told BBC Sport. “We should appreciate it, embrace it and have a great time.
“Isn’t it great that everyone from around the world is tuning in and people will be saying ‘that’s in Britain’. We are the envy of the boxing world.”
Parker, by comparison, has not competed in front of more than 10,000 fans on any one night as a pro and this payday, rumoured to be close to £7m, will dwarf anything he has earned before.