Usyk had been pushing to battle Tyson Fury earlier than talks fell aside and Londoner Dubois stepped in because the Ukrainian's subsequent title challenger in Wroclaw, Poland.
The 25-year-old is bidding for a fifth straight win since his shock defeat by Joe Joyce. Usyk, in the meantime, is undefeated in 20 skilled fights — his final two had been towards Anthony Joshua — as he places his IBF, WBA and WBO heavyweight belts on the road.
Warren mentioned: "Daniel has got more experience than some guys who have won world titles. Usyk is a great fighter and was a great cruiserweight, but he's now at Daniel's weight.
"Daniel is coming into the lion's den, that is what it's about. He's going to go in there and throw bombs. I'll be the bag provider carrying the belts again for Daniel."
Dubois is the clear underdog but said he was primed to cause an upset in front of a partisan crowd for Usyk, Wroclaw boasting a big Ukrainian population.
"I've suffered in coaching camp and I'm prepared now," said Dubois. "I've left no stone unturned for this battle."
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