De la Hoya (left) v Pacquiao is billed the "Dream Match"
Oscar de la Hoya said he had trained for "King Kong" ahead of Saturday's super-fight with Manny Pacquiao.
America's De la Hoya faces Pacquiao at welterweight in Las Vegas, two divisions higher than the Filipino superstar has ever fought at before.
Six-weight world champion De la Hoya has fought as high as middleweight.
"If you think, 'oh, he has no power, he has no speed, he's smaller', then everything can go wrong for you," said De la Hoya. "I trained for King Kong."
Pacquiao scaled 142lb at Friday's weigh-in, well below the welterweight limit, while De la Hoya, who says he has been down to the 147lb welterweight limit for weeks, was 145lb.
De la Hoya added: "This type of fight calls for a knockout. I may box, but if Manny Pacquiao hits me with a good shot, let's fight."
The fight at the MGM Grand has been billed the "Dream Match", although some have derided it as little more than a freak show.
The 35-year-old De la Hoya has not fought at welterweight since 2000, while four-weight world champion Pacquiao, 29, is a former flyweight world champion who has never campaigned higher than lightweight.
However, Las Vegas bookmakers suggest Pacquiao has a chance, installing him as an 8-5 underdog, and the man himself has no doubts he can pull off an upset.
"If you sacrifice and dream about a fight, you can win," said Pacquiao, who has 47 wins (35 KOs) and three defeats from 52 fights.
"It's going to be boxing history if I win this fight. I believe my power and my speed can beat him. Even when I'm fighting at lightweight, I'm sparring with middleweights.
"Physically , I feel the same. My speed is still there. I respect Oscar, he is a good fighter, a great warrior in the ring, but I'm not worried about his power."
It's going to be boxing history if I win this fight
For De la Hoya, who has 39 wins (30 KOs) from 44 fights, a win would help turn round a career that has been stuck in neutral for the past five years.
He has lost three of his last six fights, including defeats to Shane Mosley, Bernard Hopkins and Floyd Mayweather Jr, and was very lucky to get a decision over Germany's Felix Sturm in 2004.
His bout against Pacquiao is being looked upon as a barometer for the American fight game, which has been struggling to attract pay-per-view customers in the current financial climate.
Bernard Hopkins v Kelly Pavlik in October only managed 190,000 buys, while Joe Calzaghe v Roy Jones Jr pulled in a reported 225,000. Even at $55, American network HBO will be hoping for twice that number on Saturday.
The winner of De la Hoya-Pacquiao could fight Manchester's light-welterweight king Ricky Hatton next summer.