A lot of people believe the outcome is already pre-determined, and team Manny Pacquiao is now towing the same line ahead of the fight against Jeff Horn.

Pacquiao's trainer Freddie Roach predicted that the world title fight with Jeff Horn will be "short and sweet" with a knockout likely, as his Australian challenger said he was "ready for war".

The legendary Filipino, one of the greatest fighters of his generation, is widely tipped to triumph over the unbeaten Horn in front of an expected 50,000 people at Brisbane's Suncorp Stadium on Sunday.

"He (Manny) doesn't like to predict knockouts and so forth but I think it is going to be short and sweet," trainer Freddie Roach told reporters at a press conference ahead of the World Boxing Organization (WBO) welterweight bout.

"I think it won't last too long and someone will get knocked out."

Roach suggested the fight was a stepping stone for the eight-weight world champion to secure a rematch with American rival Floyd Mayweather, who outpointed Pacquiao in the "Fight of the Century" two years ago.

Horn's camp hit back, with the former school schoolteacher's promoters taking a dig at Pacquiao for spending most of the press conference looking at his mobile phone.

"Not only is Manny Pacquiao an eleven-time world champion... he is also a world champion texter, because he never gets off his bloody phone," Dean Lonergan said.

Horn's trainer Glenn Rushton accused Pacquiao's camp of underestimating his 29-year-old challenger and said the so-called "Battle of Brisbane" would become the "fight of the year".