Gallen declared Hunt a rattled man after the Super Samoan lashed out at the rugby league great during an explosive weigh-in on Tuesday.

Hunt's left hook failed to find its mark but Gallen admitted to being "shocked" before landing his own pre-fight psychological blow.

"I saw every part of it coming, too. Just like I'll see every part of it tomorrow night," Gallen said.

"I found it quite funny. I think he's feeling the pressure.

"I said from the start I'm going to shock everyone and embarrass him and for a bloke who's been involved in the sport for 30 years, he's under pressure.

"I've had him rattled from the start. I've had him rattled in every way."

Unbeaten in 10 fights, Gallen is surprisingly the bookmakers' underdog against the 46-year-old, who lost his only two previous boxing matches, the last of which was two decades ago.

"He's still Mark Hunt," Gallen said.

"At the end of the day, he's still fought all around the world for a long, long time and I've still got to respect his power and his experience."

Gallen weighed in under 104kg, with Hunt hitting the scales at 127.14kg.

"He was actually a bit lighter than I thought he was going to be. I expected him to come in over 130," Gallen said.

"He looks in good shape."

Adding the unpredictability, the former NSW State of Origin and Cronulla premiership-winning NRL captain said he was unsure how Hunt would approach the fight at Bankwest Stadium.

"I don't know what to expect," Gallen said.

"I don't know whether he's going to come at me first round and try and take me out in one round or whether he's going to try and box a little bit.

"I really don't know. It's probably going to take me a round or two to figure him out. I just can't get caught out early on."

Australian Associated Press