"Every time I step into the octagon is the biggest fight of my career," says Whittaker, as he prepares for UFC 213 in Las Vegas.
"This is the biggest fight of my career to this point and I can't think about the next fight, without having fought this one."
Born in South Auckland to a Maori mother and Australian father, Whittaker's family moved to Sydney in his first year and dad Jack enrolled him in karate as a kid.
Several years later, he progressed to hapkido under current coach Henry Perez and when his mentor switched to mixed martial arts, Whittaker followed him, soon making an impact on the Australian scene with his aggressive style.
His career really took off in 2012, when he was chosen for The Ultimate Fighter reality TV show, which pitted Australian combatants against British rivals in two weight divisions. Whittaker achieved the "knockout of the season" in his opening bout and made his UFC debut in the season finale, where he won the welterweight title by unanimous points decision.
But perhaps the turning point of his career came in 2014, when he moved up to the middleweight division.
"I decided to make the change because the cut for me to make [welterweight] was just too much," he reflects. "I made the decision to go up primarily for health reasons, but also to enjoy the sport a little bit more.
"It's a much better division for me. I'm stronger, a lot less weight to lose, better chin, tougher, and I enjoy the camp and process a lot more."
Since then, Whittaker has gone unbeaten in six bouts, including two Fight of the Night awards and three Performance of the Night bonuses, culminating in April's second-round technical knockout over Brazilian veteran Ronaldo Souza in Kansas City.
At 37, Souza has been an eight-time world jiu-jitsu champion and a highly-rated MMA exponent for well over a decade. The day before his loss to Whittaker, he signed a five-year extension to his UFC contract, but within 24 hours, wore egg - and blood - on his face.
"Beating Souza meant everything to me," says Whittaker, 26. "I respect him as one of the highest calibre of fighters. He has been in the top tier of the middleweight division for numerous years, so to get a win over him was absolutely massive for me."
The result promoted Whittaker above Souza into the No3 ranking among UFC middleweights, but this week, he faces the man atop that list.
Romero, 40, is a former freestyle wrestling world champion and 2000 Sydney Olympic silver medallist. He is also unbeaten (8-0) as a UFC middleweight and his victims also include Souza, whom he defeated by split decision in December 2015.
Whittaker and Romero have both beaten Americans Derek Brunson and Brad Tavares previously - neither went the distance against Whittaker, but the Cuban needed a unanimous decision against Tavares.
"Now is my time," insists Whittaker. "It's a great point in my career for this fight to happen, because I'm young enough to bounce back, no matter what happens, but also just to fight this calibre of fighter is going to be absolutely massive.
"The key to beating him is just me being me. I need to go out there and use my strengths - my striking ability - to control the fight, dictate the pace and push the fight where I want it to go."
Given Romero's background, Whittaker needs to avoid a grappling contest that takes him out of his comfort zone and into his opponent's sweet spot.
Lying in wait is Bisping, who has dodged Whittaker once before, in November 2015, when he pulled out of their scheduled meeting with an elbow injury, before going on to capture the world title last December.
For his part, the Englishman believes Whittaker will prevail over Romero, whom he believes is prone to powerful, but wild punching.
"Yoel is going to start strong, he'll look to land bombs," says Bisping. "He'll look to get a takedown.
"Problem is he swings wildly.
"He's not an accurate striker, he's not a polished striker ... he's a wrestler with insane power," says Bisping.
"With that insane power, you can get a lot of knockouts, of course you can, and he's capable of throwing kicks or throwing a flying knee and getting a knockout."
But Bisping believes this style will take a toll on Romero and if he can't finish the fight early, Whittaker will pick him apart.
