Speaking from his own "terrifying" experience, Nikita Tszyu has laid bare the frightening proposition that will confront trash-talking Tony Harrison in next month's world title bout with Tim Tszyu.
Harrison (29-3-1, 21KO) and Tszyu (21-0, 15KO) will joust at Sydney's Qudos Bank Arena on March 12 for the interim WBO super-welterweight belt.
The winner will face undisputed world champion Jermell Charlo later this year for all four straps after the Texan broke two bones in his left hand before his scheduled showdown with Tszyu last month in Las Vegas.
Harrison is the only man to beat Charlo and can't believe Tszyu is risking everything by taking him on when the Sydney slayer could have waited for Charlo to recover.
"We need to talk to management about this one. We need to go to HR. Something ain't right about this one," Harrison said last week, having previously dismissed Tszyu as little more than a "park fighter" who had been beating up on lesser-skilled Australians to build his undefeated record.
However, the mild-mannered Tszyu has heard it all before and warned Harrison he is a very different, deadly beast once inside the ring.
"I turn," Tszyu said.
And Tszyu's younger brother Nikita, having spent hundreds of hours sparring with his sibling idol, can vouch for that.
"There is that switch," Nikita told AAP.
"Tony Harrison, he has no idea what he's getting himself into.
"You can only experience it once you're in the ring with Tim, once you're closed off.
"There's just you two and the referee in there and there's hundreds of thousands of people around you, watching you in this battle and this person (Tszyu) is there with this intention of just trying to destroy you and that look in his eyes makes things, yeah, really real.
"I don't really ever get scared when I'm sparring or when I get into fights. I'm more just in the zone.
"But that look in his eye, it's a terrifying thing."
Nikita dubbed Tszyu "The Terminator" after their brutal training lessons.
"It's hard to come forward against Tim," he said.
"I remember the last time we sparred, any time I'd crack him with a clean shot, usually you'd see your opponent move back and go for a little bit of a recovery.
"But that kind of fired up something inside of him and pissed him off. He was coming forward straight away, so I was always like hesitant to hit him hard, or try and get him again because it was scary. It's honestly terrifying.
"He'd just destroy me. I'd get like one clean shot in and then I'd cop like 10 or 12."
Also undefeated in his four professional bouts, Nikita Tszyu will fight Tasmanian Bo Belbin on the March 12 undercard.