Gold Coast-based Kiwi Dylan Andrews (17-6, 1 NC) and England's Brad Scott (9-3) both weighed 185 pounds ahead of their middleweight meeting.
Whittaker has plenty to gain from his fight tomorrow given Tavares sits at 14th in the divisional rankings while the Australian is unranked.
"I have no idea about that sort of stuff. That's beyond me, but yeah I don't know why they underestimate me so much. You know, I encourage it," Whittaker told Submission Radio.
"Underestimate me and I'll flip you upside down, but it might be because we live in Australia and I don't really leave my house much."
Whittaker made his middleweight debut in impressive fashion with a second-round TKO win over American Clint Hester (11-4) at UFC Fight Night 55 in Sydney in November after moving up from welterweight.
"Yeah, you know being in the middleweight division is where I belong. This is my home now. Moving back down to welterweight isn't an option, and yeah I'm here to stay. This is my sport."
That battle with Hester was a 'Fight of the Night' special, which netted Whittaker a US$50,000 bonus and he'd love more of the same with a win over Tavares tomorrow.
"I know I can finish him, it's just a matter of when. Whether it's in one minute or 15, it doesn't bother me. I'm going to go in there and I'm going to throw everything I have at him, and if he can handle it, good on him," he said.
"I think it's definitely going to be a stand-up battle. The only time it won't be is if he decides that he doesn't want to."