Though Pacquiao has won world titles in an unprecedented eight weight divisions to cement his status as the best pound-for-pound boxer, he delivered one of the least impressive performances of his career in his most recent fight.
The Filipino southpaw narrowly retained his WBO welterweight title with a controversial majority decision over Juan Manuel Marquez in November after his preparations had been hampered by various distractions, including marital difficulties.
Pacquiao has since patched up his relationship with his wife Jinkee and become a much more disciplined boxer after replacing his former pastimes of cockfighting, gambling and nightclubbing with increased bible study and family time.
"No more gambling, no more drinking," the 33-year-old Pacquiao told Reuters while preparing for Saturday's bout, which is scheduled for 12 rounds at the MGM Grand Garden Arena.
"I just want to focus on my career, focus on praying and follow the commandments of God."
Asked what had gone wrong for him against the experienced Mexican Marquez, Pacquiao replied: "Not all the time I am going to win with a good fight. Sometimes a fight comes where I will win after a hard time, and that time was in the last fight.
He then added: "I was in 100 percent physical condition for that fight but I did have some family issues that I had to deal with. I also underestimated him."
Pacquiao's respected trainer, Freddie Roach, has no doubt that his fighter, who has been installed by Vegas bookmakers as a 4-1 favourite, will be back to his best with a disciplined display against Bradley.
"I am very happy with Manny's focus," the bespectacled Roach told Reuters. "His focus is the best I have ever seen. Manny has got rid of a lot of distractions in his life and he has some new distractions that are a lot better than the old ones."
While Roach respects the muscular Bradley, he is not banking on the American going the full distance against Pacquiao who has a career record of 54-3-2 with 38 knockouts.
"Bradley comes forward and is very aggressive," said Roach. "He is a well-conditioned athlete and we know we are in for a tough fight. I don't think we have fought anybody that muscular.
"But I think he will be overwhelmed by Manny's speed and power. It's going to be a great fight as long as it lasts. Manny wants to prove he's not all done like some people say."
Bradley (28-0, 12 KOs) will be fighting for only his second time at 147 pounds but he firmly believes he has a much greater incentive than his opponent.
"I'm going to put it all on the line on Saturday," said Bradley, who won his first world title at light-welterweight by defeating Britain's Junior Witter in 2008. "This is not his biggest fight, it's my biggest fight. It's all or nothing."
The eloquent and eminently likeable Bradley was clear-cut about his best strategy against Pacquiao.
"I know that I've got to stay tight, I've got to stay behind a good jab and I've got to keep moving," he said. "I've got to have great defense and I've got to counterpunch the hell out of this guy with combinations."