And during an interview on Wednesday at the MGM Grand Hotel, surrounded by reporters with their tape recorders in his face, the man who is now considered boxing's best fighter, pound-for-pound, admitted that he once considered quitting.
"After those fights, I'll admit, I was thinking, 'Oh, maybe I'm going to stop boxing,'" said Pacquiao, 30, referring to stoppages that occurred in 1996 and 1999. "I was thinking, 'Maybe boxing doesn't like me.' But then, it became a message to me to focus more on boxing."
It's a good thing that Pacquiao did, for it led him down a glorious path toward historic achievement.
For on Saturday night, at the MGM Grand, Pacquiao (49-3-2, 37 KOs) will go after his seventh world title in a different weight class when he takes on WBO welterweight (147 pounds) king, Miguel Cotto (34-1, 27 KOs), at a catchweight of 145 pounds.
Their appearance marks a return to the site where Cotto suffered his lone defeat, a brutal 11th-round knockout to Antonio Margarito in July 2008.
It also marks a homecoming for Pacquiao, who won his second world championship at the MGM when he stopped Lehlo Ledwaba in six rounds for the IBF super bantamweight crown.
"I remember that was my first fight with Manny, and nobody wanted to fight that guy (Ledwaba). I mean, he was the most feared 122-pound guy in the world, and we knocked him out in the sixth round," said Freddie Roach, who was named the 2008 Trainer of The Year when Pacquiao also was named Fighter of The Year.
"And that was after Manny had been knocked out twice, the second time being like a year and a half before that," said Roach.
"The first time he got knocked out, he lost the title on the scales. He fought the fight anyway and got knocked out with a body shot," said Roach.
"The second knockout was a countrymen of his who hit him with a really good shot," said Roach. "Manny showed me both knockouts, and I asked him, 'do they bother you still?' He said, 'No big deal, it happened, but it will never happen again.'"
And it hasn't.
Pacquiao was 11-0 when he was stopped by Rustico Torecampo, and, 26-1, before losing to Medgoen Singurat.
"I was overweight in those two losses," said Pacquiao. "I was losing too much weight, and a lot of times, I just had no energy."
Not long afterward, Pacquiao "walked into" Roach's Wild Card Gym, in Hollywood, Calif., a raw, skilled, athletic and powerful fighter.
"Everyone had turned him down, that's the funny thing about it. So when he came to America, and he stopped at my gym, I said, 'I hear you're pretty good with the mits,'" said Roach.
"Manny's manager says, 'can you catch him?' And I did," said Roach. "And after one round of mits, he went to his manager and he said, 'We have a new trainer.' We hit it off right away. But I never dreamed that it would get this big. But I love it."
Pacquiao considers his two most rewarding victories, those over Oscar De La Hoya and Ricky Hatton, respectively, by eighth, and, second round knockouts in December and May of 2008, and 2009.
Along the way, however, he has vanquished Mexican greats such as Marco Antonio Barrera, Erik Morales and Juan Manuel Marquez, earning him the nickname, "The Mexicutioner."
Although much has been made by Roach of Cotto's loss to Margarito, whom he insists has "taken a lot out of" the Puerto Rican star, Pacquiao still believes the champion to be a major threat.
Cotto, said Pacquiao, proved himself in his last bout with Joshua Clottey, overcoming a deep gash over his left eye to pull out a closely fought decision in defense of his title.
"When I saw and studied his fight against Clottey, he's still a good fighter," said Pacquiao. "He's still the same fighter, still strong, and still can fight, even though it is tough to come back from a knockout."
Pacquiao should know, for he speaks from experience.