Manny Pacquiao (57-6-2) has joked that a knockout against Timothy Bradley -- who has twice gone the distance with the Filipino, winning one, losing one -- would boost his appeal at the ballot box when he stands in Filipino elections in May.

Pacquiao however has not scored a knockout since 2009, when he demolished Britain's Ricky Hatton in two rounds before beating Miguel Cotto six months later with a 12th round TKO.

Bradley said he expects Pacquiao to adopt an aggressive game plan. They collide for a third time on Saturday at the MGM Grand in Las Vegas.

"I'm expecting him to be more aggressive, he's going to come out like a bat out of hell and try to take my head off," Bradley said.

The 32-year-old from the Californian desert city of Palm Springs believes, however, that a combative approach from his opponent could play into his hands.

"If he's more aggressive, then it's probably going to give me more opportunities I would think," Bradley said.

Roach however insisted Pacquiao would walk the line between controlled aggression and outright foolhardiness.

"We're professionals, we won't make that mistake," Roach said. "We're not going to go in there looking for a knockout. We've never looked for a knockout because if you do it will never happen. The knockouts come as kind of a bonus but we never look for them out there."

Pacquiao meanwhile shrugged off reports that Bradley had sought to incorporate tactical elements used by Juan Manuel Marquez when he inflicted a devastating sixth round knockout on the Filipino in December 2012.

"I know that Floyd (Mayweather) used the same sparring strategy, I know that they're going to use that strategy," Pacquiao said. "But I learned a lot from that fight. So maybe they should think about another strategy."