German boxer Rico Mueller expects his Australian opponent Jeff Horn might have some issues as he faces a late scramble to make weight for Friday's crucial welterweight clash.

Mueller is at 67kg [147.7] ahead of Thursday afternoon's weigh-in but Horn is at 70.5kg [155.4] and must drop a whopping 4.5kg [9-pounds] before the bout, which is effectively a world title eliminator with the IBF welterweight championship expected to be vacated soon.

"He'll be very busy in the next 24 hours losing his weight and he might have some problems," said Mueller, who has a 20-1-1 record and has not tasted defeat in six years.

Like Horn, the 28-year-old Mueller could propel himself into the No.2 spot on the IBF world rankings with victory at the Sleeman Sports Complex in Brisbane.

Mueller, a defensive counter-puncher, has 14 career knockouts to his name but said he'll take a won over the undefeated Horn to matter how it comes about.

Horn is planning to crack through Mueller's defence with an all-out body assault and in preparation been firing off shots into a special body protector worn by his trainer Glenn Rushton.

An all-business Mueller, however, was in no mood to talk tactics with reporters on Tuesday.

"I won't tell anything, you'll have to wait until Friday for that," he said.

Mueller's trainer, former pro boxer Michel Trabant, said it was the most important bout of his career.

"It's basically all or nothing, especially in terms of the world title," he said.

"Rico hasn't lost in a very long time, he's trained very hard and he's in great form. That's why I'm so confident he'll win."