The Liverpudlian faces the highly-rated and undefeated Ukrainian Oleksandr Usyk, holder of the WBA, WBC, WBO, IBF and Ring magazine titles, at Manchester Arena.
Bellew is stepping back down from the heavyweight division for what could be his final fight in the hope of fulfilling his dream of becoming undisputed world champion.
Asked if he was facing he best opponent yet, the 35-year-old said: “Yes – he is the ultimate test. There is nothing this man cannot do in a boxing ring.
“He is the most complete fighter I have ever faced. Everything he does is class.
“I meet a man who has exceptional skills, an exceptional talent. He has everything I have except that one thing – I can turn someone’s lights out in the blink of an eye.
“It’s never happened to him before but it could happen on Saturday. I am going to find a way.”
Usyk, 31, is an Olympic gold medallist and unbeaten in 15 fights as a professional. He is expected to step up to heavyweight in the near future and has his eyes on Anthony Joshua’s titles.
Bellew has won 30 of his 33 fights, the two most recent being his heavily-billed bouts against David Haye in the top division.
He briefly retired after the second of those in May but was quickly tempted back into the ring by the opportunity to face Usyk.
“I have to beat him up, or find a way to do the impossible,” he said.
“The only chance I have is a puncher’s chance – I cannot outbox this man. He is a formidable opponent. He has everything any boxer could possibly want and he is a horrible southpaw.
“But I’ve shown what I can do at heavyweight and, believe you me, I will show even more what I can do at cruiserweight. I am faster, sharper and possibly even stronger at cruiserweight.
“As good as he is, as great as he is, he is meeting someone with something inside him.
“I don’t know what I am going to do, when I am going to do it, but I just know I am going to punch him in the face really hard.”
Usyk, sitting alongside Bellew, was more understated.
“Tony is my best opponent ever, definitely. We feel Tony and I will perform our best. I think it will be a spectacular fight,” he said.
“Years ago I dreamed about visiting England. I couldn’t imagine that some day I would be fighting in Manchester. I am as glad as the small kid who received a Kinder Surprise!”