Mueller, who has never been knocked out, has been training this year with Manny Pacquiao's coach Freddie Roach, a member of the World Boxing Hall of Fame.

"I had a little look at him last night. He's going to be able to last a lot longer, he's going to have good fitness, good defence, he throws good combinations," Horn said.

"I've just got to use my movement against him and I'll be fine."

It is the start of a more intensive program for the 28-year-old former schoolteacher, who will fight every two months from October in an attempt to build a national profile.

"Danny Green and (Anthony) Mundine have been around a long time, they've done good for boxing. But there are new people coming through now and I think I will be the person to watch when these guys finish," Horn said.

Confirmation of Horn's latest assignment comes at an interesting time in welterweight boxing, with talk current IBF title holder Kell Brook may switch permanently to the middleweight division and vacate his belt.

Brook suffered a broken eye socket in his first career loss on the weekend to Kazakh middleweight Gennady Golovkin.

If he left the division, that could put Horn within touching distance of a bout with up-and-coming American Errol Spence Jr., one of only two fighters ahead of him in the rankings.

"In a perfect world, Jeff will be of equal stature and they can have a long-running rivalry over the time they're in the game," promoter Dean Lonergan said.

In the WBO, Manny Pacquiao - who is three spots above Horn - takes on champion Jessie Vargas for the title in Las Vegas in November.

Horn is anything but peturbed by the lofty company he now finds himself in.

"There is pressure but I thrive for the pressure. I love competition, my friends and family will tell you that," he said.

"All I want to do is win, and that's the plan."