The greatest boxers of their generation met accidentally in January when attending a Miami Heat basketball match, chatting briefly as they came face to face for the first time before exchanging phone numbers.
Mayweather called Pacquiao a few hours later and visited the Filipino in his hotel suite in what has since been described as the turning point in ending the five-year stand-off that had prevented the welterweight rivals from clashing.
It was during those discussions that Mayweather, who stands one and a half inch taller and possesses an extra five inches in reach, detected an element of concern in Pacquiao.
“You can read a guy’s body language. When Pacquiao first saw me in Miami, he didn’t expect to see me over there at the basketball game,” Mayweather said.
“He looked shocked, like – ‘damn, he’s taller than me. He’s bigger than what I thought he was’.
“Just by being in the sport for so long, you’re able to read body language and to read a fighter’s eyes.
“Normally when I face an opponent, they outweigh me by 17 to 20 pounds on fight nights. This has been going on for a good while now.”
Beyond his claim to being better than all-time greats Muhammad Ali and Sugar Ray Robinson, Mayweather has been relatively quiet in the build-up to a fight that could generate as much as #332million.
The unbeaten 38-year-old, who stands to earn #100million for his outing at the MGM Garden Arena, insists the bombastic self-promotion that has made him a love-hate figure has served its purpose.
“Even from day one I said I wanted to work extremely hard to get to a certain point in my career and to be the first fighter to ever make nine figures in one night,” he said.
“It took a game plan for me to go it alone. It was me speaking out with a very, very loud voice and having a lot of personality. But as you get older, you mature.
“After trash talking for 17 or 18 years and constantly saying ‘look at what I’ve done, look at me, look at me, I’m the best’, I’m now at a point where I can say ‘it is what it is’.
“I did all that loud talking and everything to get to a certain point. I’ve still got a lot of personality, but I did what I had to do to get to a certain point in my career. It was a brilliant game plan.
“I know what I can do. I know what I bring to the table. God has truly blessed me to be in this situation. I have a good team. My children are healthy, so I don’t have to do all that.
“When I come home, I leave boxing at the boxing gym. When I go to the gym or when I go to train, I work. I dedicate myself to my craft.”
Mayweather starts as a strong odds-on favourite with a points victory the most widely tipped result.
Pacquiao must stretch his mind back to 2008 for the last time he was expected to lose, but on that occasion he responded by bewitching a weight-drained Oscar De La Hoya over eight one-sided rounds.
“I’m not worried at all (about being the underdog). It’s good for me because it gives more motivation, encouragement and focus to win the fight,” Pacquiao said.
“It’s been a while since I was an underdog in a fight….since 2008.”