By Edward Chaykovsky

WBO welterweight champion Manny Pacquiao is promising a more serious approach to his trilogy bout with Juan Manuel Marquez on November 12th at the MGM Grand in Las Vegas. After going to a controversial draw in 2004, and winning a controversial split decision in 2008, Pacquiao wants to erase any possible doubts.

His trainer, Freddie Roach, is advising him to leave compassion at the door. Roach wasn't happy with Pacquiao's "good guy" approach in his recent fights with Antonio Margarito and Shane Mosley. For the last few years, Marquez led a widespread campaign with claims of being robbed by the judges in their two previous fights. Pacquiao wants to shut Marquez's mouth for good.

"This time I have less compassion for my opponent. Yeah this is a kind of personal," Pacquiao said to the New York Daily News. "But you still have to do your job. I have to prove that I'm doing right in my job."

One of the main differences in their fight is not the higher weight limit of 144-pounds. The right hand, says Pacquiao, is the big difference. In their two prior meetings, Pacquiao was left-hand happy and rarely used the right.

"After the Marquez fight I fought with [David] Diaz," Pacquiao said. "After the Diaz fight we planned to fight in another weight division and moving up. We began to think about how to improve my style and improve my power. So we developed the right hand so we can use it against a big opponent."