That meant Whittaker (16-4) and Brunson (16-3) were pushed in to the bright lights and it will mark the first time the Auckland-born Whittaker has been the headline act in the UFC.
"It was always a goal when I first entered the UFC," Whittaker said of the main event slot.
"It's another fight. It's the same fight. I just get to fight later on the card. It's a huge honour though to headline an Australian card."
While he was born in New Zealand, Whittaker moved across the Tasman as a child and calls Sydney home with his wife and son.
He has another boy on the way in about three weeks and he said becoming a father helped influence his perspective as a fighter.
"It's changed my entire life. It's changed my family life, it's changed my attitude. It's changed my career."
Change is also a strong theme of his bout with Brunson because the winner of this fight will likely change their path in the UFC towards a title fight.
Cuban Yoel Romero (13-1) looks to be the next challenger for champion Michael Bisping (30-7) but Whittaker or Brunson will also be near the front of the queue with a dominant performance this week.
Whittaker turns 26 next month and is in no rush to demand a title opportunity but at No 7 in the rankings, The Reaper has carved an impressive trail through the middleweight division since he moved up from welterweight in 2014.
His mixture of strong takedown defence and impressive kickboxing has helped him rack up signature wins over the likes of Brad Tavares (14-4) and Uriah Hall (12-8).
But Brunson, who is pegged at No 8, has possibly been more impressive of late given his past four wins have all come via first-round knockout inside three minutes.
The former three-time Division II All-American wrestler from the University of North Carolina at Pembroke hasn't been fighting scrubs either and his knockout power is always a threat.
As is regularly his plan, Whittaker will want to keep the fight standing so he can utilize his more refined striking.
Brunson's wrestling and grappling look to be one area where he has an advantage over Whittaker but the Sydneysider defends 93.1 per cent of takedown attempts against him.
"Derek's a tough fighter, he's in the top 10 for a reason," Whittaker said. "I respect his abilities."
While this Sunday's fight will only be his second in 2016, Whittaker said the extra time spent in the gym had been beneficial for him.
"I've made improvements across the board and every time I step in that octagon you will see the best Robert Whittaker."
On the undercard, Kiwi featherweight Dan Hooker (13-6) will meet American Jason Knight (14-2).
