Floyd Mayweather claims his long-awaited showdown with Manny Pacquiao isn’t a battle between good and evil as the two rivals went eyeball-to-eyeball at their final pre-fight press conference for the richest fight in history.

“I am a realist,” said Mayweather whose a 47-0 record has made him the highest-paid sportsman on the planet.

“This fight is not good versus evil. It is one fighter who is at the top and another.”

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Pacquiao, a two-term congressman touted as a potential future president of the Philippines, is beloved as a humanitarian in his native land.

A devout Christian who has put womanising and gambling days behind him, he said his main aim in taking on Mayweather was to inspire the weak and glorify God.

Mayweather, an energetic trash-talker in his younger days, hasn’t been afraid to compare himself to Muhammad Ali, or to flaunt the perks his wealth.

Nor is he a stranger to using his fists outside of the ring, serving jail time for one of several incidents of domestic violence.

But none of that will matter on Saturday, when the two climb into the ring at Las Vegas’ MGM Grand Garden Arena.

“I believe in my skills. I believe I will be victorious,” said Mayweather, who puts his WBC and WBA welterweight belts on the line against the WBO champ who boasts a record of 57-5-2.

For more than five years, contractual hurdles and animosity between the camps kept the top pound-for-pound fighters of their generation from meeting.

But now the long-awaited bout is set to break all of boxing’s revenue records, capturing the imaginations of fight fans and casual observers around the world.

“I don’t take nothing away from Pacquiao, he is going to be an intriguing match-up on Saturday,” Mayweather said.

“He didn’t get to where he got by not beating tough opponents.”

It’s that kind of measured respect that has Pacquiao trainer Freddie Roach doubting that Mayweather’s heart is in a fight from which he stands to make $US200 million.

“I wonder if he’s going to show up,” Roach said shortly before the fighters took the stage at the MGM Grand’s 1,950-seat Ka Theater.

Former heavyweight champion Mike Tyson strolled in, only one of the boxing legends, A-list celebrities and casino high-rollers drawn by the buzz surrounding the fight.

But the pre-fight festivities have offered few fireworks.

“I think he was forced into this fight,” Roach said, adding that he thought Showtime pushed Mayweather into the bout.

“I don’t think he wants to fight this fight. He didn’t get to pick his opponent.”

But the 38-year-old said he just doesn’t need to indulge in the kind of brash talk that was the hallmark of his younger days.

“From the beginning of my career I have always had a game plan,” Mayweather said. “I make calculated moves in the ring and out of the ring. Me speaking loud and having personality I did that in the past.

“I’m a lot older and wiser, this fight sells itself. I don’t have to do it.”