Internationally recognised boxing powerbroker Gary Shaw says Australia's Daniel Geale heads into his middleweight boxing unification bout with Germany's Felix Sturm as one of the world's most under-rated fighters.

IBF champion Geale and WBA Super title holder Sturm will put their respective belts on the line in Oberhausen, Germany early Sunday (AEST).

Geale has a relatively low global profile because he has yet to have a professional bout in the United States, the epicentre of professional boxing.

"I think Daniel Geale is one of the most under-rated professional fighters today in boxing and certainly under-rated as a world champion," said American promoter Shaw, who is also Geale's international manager.

"Because of that he doesn't get his due as to how good he is technically as a boxer.

"Since I've been with the team I've seen improvement each and every fight.

"Those of us inside boxing know how hard it is to go to Germany and fight and come back with a win, no less lift the world title off a current champion, which he did with Sebastian Sylvester.

"I believe he'll do the same thing on Saturday night, that he'll come back as a unified champion."

Shaw pinpointed three keys to a Geale win.

"In previous fights I've seen him lower his hands, so he needs to keep his hands up," Shaw said.

"He needs that good head and upper body movement and must fight all three minutes of each and every round."

He said Geale's trainer, Graham Shaw, was also very under-rated.

Geale's corner also includes vastly experienced cutman Brian Wilmott, who has worked over 20 world tittle fights, assisting among others, Jeff Fenech, Jeff Harding, Danny Green, Billy Dib and Joe Bugner.

Both fighters weighed in comfortably inside the limit on Friday.