It has been announced that Harrison and Wilder will meet in Sheffield on April 27, and while the former European champion feels that he can beat the knockout specialist, he has admitted he will retire if he suffers defeat.
The 41-year-old told Goldenboy Promotions: "Deontay is a fast, dangerous puncher, but he has not been tested as a pro.
"I have lot of respect for him, so it's not personal, but this is the door I must walk through. Lose and it's over, win and I'm in the top ten for sure, eligible to challenge for the world title.
"Biggest risk, for the biggest reward. It can't get any better than that."
Wilder is unbeaten in 27 bouts, all of which have been won inside four rounds.