Boxing trainer Freddie Roach is urging Manny Pacquiao to regain his old “killer instinct,” especially for his upcoming fight against Juan Manuel Marquez. Roach instructed the Filipino champion to knock Marquez out as soon as he gets the chance, according to DogHouseBoxing.com. “Don’t be a nice guy. See what happens to nice guys like Victor Ortiz? Manny, don’t let this fight go any longer than it should,” said Roach. The boxing coach was referring to Ortiz’s knockout defeat to Floyd Mayweather Jr. Mayweather knocked Ortiz senseless while the latter was apologizing for an intentional head butt. Roach said he received assurance from Pacquiao that the fight will end with a stoppage. The boxing trainer earlier voiced his concern that Pacquiao had become compassionate to his recent opponents. He said that this was the reason Pacquiao failed to halt Antonio Margarito and Shane Mosley. But Roach said fans might see a different Pacquiao in the coming Marquez fight. “When Marquez wore the t-shirt that said, ‘I Beat Manny Pacquiao Twice,’ that was a slap in the face. Manny will never say it but he doesn’t like this guy. I can tell. He has a little sparkle in his eye,” said Roach.