The Filipino's trainer believes it's a possibility. "I'm going to give Manny Pacquiao a really hard fight".
Pacquiao has been under tremendous pressure coming from his longtime trainer Freddie Roach, adviser Michael Koncz and strength and conditioning coach Justin Fortune. "But if he struggles in this fight, it could be over", Roach said.
Although Pacquiao is eager for redemption after suffering defeat in the "fight of the century" back in May 2015, he's not letting the prospect of a rematch interfere with his preparations for this weekend's bout.
"I'm so thankful for this great opportunity to be here in Australia and fight here, and the warm welcome of the people here", Pacquiao said.
"I don't want their judgment affected by the excitement of the fight in the heat of battle". We don't want to underestimate Horn thinking about another fight. This fight is not done yet.
"We are getting close to the end I know".
"I made my other son Ben (27) watch it with me because he will be in Jeff's corner on Sunday and I wanted him to realise that no matter what, they all have to take care that Jeff does not get badly hurt".
Before leaving the gym, Pacquiao signed some souvenirs and took photos with Australian fans, who patiently waited for him to finish his training.
While Horn has age on his side - at 29 he's nine years younger than Pacquiao - the fight represents an vast leap in class for the Brisbane challenger, who has quit his former life as a school teacher for what can only be described as a dream opportunity against an all-time great. "I know what he's feeling - being there, being the underdog". "I am looking for a big win here", Roach said.
It marked the only time that a Pacquiao-Marquez bout had a definitive result as their previous three fights all ended in inconclusive decisions.
"I'm doing numbers in my head all the time on how much punishment he might be taking - how he's going mentally, how he's coping".
Asked specifically what the fallout would be if Horn (16-0-1, 11 knockouts) somehow won, Roach said "depending on how he lost, I would probably encourage him to retire". "Also I'm a teacher in the ring so..."
Man to face court over fatal NSW shooting
NSW Police investigators will seek to extradite the man from Queensland when he appears at the Southport Local Court Later today. Drug enforcer Ace John Anthony Hall, 31, was sent to the facility in Thornlands, southeast of Brisbane, in May.