The Pacquiao-Horn bout looms as the biggest fight in Australian boxing history and the 11-time world champion has spent the week promoting the "battle of Brisbane", which is expected to attract an attendance record at Suncorp Stadium.

It pits the Filipino superstar, who is enjoying his third reign as WBO welterweight champion, against the 2012 London Olympian, who boasts 16 wins and a draw from his 17 professional fights.

"Jeff Horn, we're coming, and we're coming and looking for a knockout, so be ready," Roach told Fairfax Media from his boxing gym in Los Angeles.

"We're not going to take anyone lightly; we never have and we never will.

"[Horn is] not very well-known, but the thing is, I've seen his last few fights he's won by knockout, and he's pretty impressive, a pretty good puncher and I hope he does come with that style and comes looking for a knockout.

"Horn looks like he's a little bit of a puncher. One thing about Australian fighters is he'll definitely be in shape – they work hard, their work ethic is good. I've seen a lot of Australians in my gym. I actually have three permanently right now."

Roach knows the Filipino better than most, and still recalls the day a young Pacquiao strolled into his gym for the first time 17 years ago, a day the highly reputed coach says his life changed.

He'd been advised not to open a gym, but his standard response to the detractors was simple.

"You never know when the next Muhammad Ali is going to walk through the door," Roach said.

"Manny Pacquiao walks through my door a couple of months later and we won our first world title together shortly after that.

"I didn't know who Manny was and he didn't know who I was. He said, 'We hear you're pretty good on the mitts'.

"After one round he looked at his trainer and said we have a new trainer, and I went over to my guys and said this guy can f---ing fight.

"I've trained fighters who are good punchers before and I've trained guys who are fast and explosive, but I never had a guy that had both. He has tremendous explosion on punches, great power.

"The first round was just unbelievable. Usually you're getting used to each other and you're missing, but me and him never missed a beat, it was like we knew each other our whole life.

"We finished the workout, then we made a deal."

Since then Roach has been in Pacquiao's corner, and plans to be until the 38-year-old hangs up the gloves.

What happens after the Horn bout is still up in the air, although a fight with unbeaten American Mikey Garcia is shaping up as a strong possibility.

Englishman Amir Khan was in the gun earlier in the year, but Roach said team Pacquiao was leaning towards Garcia.

That's assuming Pacquiao overcomes the Australian, who said during the week he was confident he could stop the world champion. Should Horn win, he'll grant Pacquiao a customary rematch, most likely in November this year.

Horn's confidence is mirrored by fight promoter Dean Lonergan.

"It's going to be an absolute war and I think at the back end of it we're going to have a brand new champion and a new legend, one that all of Australia can celebrate," Lonergan said.

"I know that's not what Manny Pacquiao wants to hear and I know it's not what [promoter] Bob Arum wants to hear, but at the end of the day it's a new guard, we're going forward."

Roach expects his ageing star to fight on beyond this year, but said retirement was looming for the veteran.

"When I tell him he's done, he will retire," Roach said.

"He's not there yet, his work ethic is so great; he trains really hard for every fight.

"He still has a couple of years left in him."