The Ukrainian is currently without a trainer after splitting with former coach, Serhiy Vatamanyuk, before claiming victory in a punishing 12-round affair against Mairis Breidis in January.
Describing the decision in a new promotional documentary ahead of tonight’s WBSS showdown against 24-year-old Gassiev, Usyk said: “Serhiy was not really my coach.
“He just helped me with some things. We don’t work together any more.
“The things he gave me were not helping me develop in any way. I don’t want to work with a person just to have someone there.
“He is a good guy – but being a good guy is not a profession.
“It is okay. I have a guy who helps me. A guy who is more experienced in boxing.”
London 2012 Olympic gold medallist Usyk has since turned to long-time cutman Russ Anber to help work on his training and technique.
The veteran boxing expert revealed the role he plays in Usyk’s preparations, saying: “In anything I do usually with any fighter I’m involved in with this position, I always would like to put my two cents worth of advice and consultation [in].
“That is my role with Usyk.
“You cannot train harder than this guy. It is impossible. He trains three times a day. Harder is not an issue. I don’t know of any people, other than [Vasyl] Lomachenko, who train harder than Usyk and I am 40 years in this sport.”
Gassiev, meanwhile, will be cornered by legendary coach Abel Sanchez – the man credited with transforming Gennady Golovkin into a pound-for-pound contender from his Big Bear training base in California.
The Russian, who is just 24 years old, is aiming to add Usyk’s WBO and WBC world titles to his IBF and WBA straps, becoming only the third undisputed cruiserweight champion in history.
Gassiev is currently priced at evens with Sky Bet, while Usyk is a 4/5 slight favourite.