MANILA, Philippines—If ever Manny Pacquiao wants to end his career in a blaze of glory, this is his chance: His biggest fight, his biggest—literally and figuratively—opponent.

Small wonder the hard-punching southern-bred southpaw is pouring everything he has in the gym to prepare for Oscar De La Hoya.

“This is probably the most difficult training I’ve had since starting my boxing career,” Pacquiao told reporters in Filipino during a teleconference in Tuesday’s PSA Forum, referring to a regimen that includes, among others, plyometrics.

“Every day, we do different things during training.”

Plyometrics is a type of exercise training designed to produce fast, powerful movements, often with the goal of increasing the height of a jump or the speed of a punch or throw.

Pacquiao is undergoing the exercise under the guidance of Alex Ariza, who is hoping to pack power and speed into a 5-foot-6 dynamo already reeking with both.

“I’m about 80 to 90 percent ready and I just need to keep up the pace of my training to make sure I’m 100 percent for the fight.”

Pacquiao and the 5-foot-10 De La Hoya, boxing’s acknowledged “Golden Boy,” trade mitts on Dec. 6 at the MGM Grand in Las Vegas in what could boil down as the year’s biggest boxing event.

Pacquiao has said that he will fight only once or twice after this, meaning this is his chance to polish a legacy that he has already carved: Being among the best pound-for-pound boxers of all-time.

“I started boxing at a very young age,” Pacquiao said. “I don’t want to be like other boxers who retired when their bodies were already too beaten up.”

The sheer size edge of De La Hoya has made this mission difficult, but the former baker’s assistant who stole a ride on a Manila-bound ferry to fulfill his dreams is no stranger to adversity.

“I love being the underdog, just as I was (in the first fight) against (Marco Antonio) Barrera,” Pacquiao said. “It makes me work harder.”

Pacquiao said he is between 150 and 151 pounds now. And although he isn’t cutting down on food intake, he sees no problem making the catch weight of 147 lb, especially since he has already won four titles in four lighter divisions.

The Gen. Santos City native thinks trainer Freddie Roach’s inside knowledge of De La Hoya—Roach trained the Golden Boy for his megabuck match against Floyd Mayweather Jr.—will help negate the size disparity.

“We’re working on one or two techniques that I can’t reveal yet,” Pacquiao said.

De La Hoya, on the other hand, hopes to benefit from having two Hall of Fame trainers. Aside from Juan Manuel Marquez honer Nacho Beristain, he has tapped the services of renowned guru Angelo Dundee.

Pacquiao, though, thinks it will be tough to incorporate Dundee’s expertise into De La Hoya’s regimen.

“They might not agree on certain things,” Pacquiao said. “But there’s still time. De La Hoya can learn something new in one month.”

“I don’t want to predict anything. I’ll sacrifice a lot to prepare for the fight.”