(CNN) -- "Sugar" Shane Mosley has vowed to knock out Manny Pacquiao when the pair face each other at the MGM Grand Hotel in Las Vegas on May 7.
Following confirmation that Mosley will challenge for Pacquiao's World Boxing Organization (WBO) welterweight title next year, the American believes the Philippine legend can be beaten.
The 39-year-old Mosley is confident despite being beaten by compatriot Floyd Mayweather Jr. earlier this year.
"Pacquiao's defense is not as good as Floyd Mayweather's defense," he told the Boxing Scene website.
"I think I can probably win a decision, but I am going into the fight to knock Manny out.
"I am pretty sure that Manny will be trying to knock me out as well -- that is why it is going to be a great contest. We are two guys who are willing to fight."
With Pacquiao's long-anticipated fight against Mayweather Jr. still no nearer to becoming a reality, veteran Mosley -- who has held world titles at lightweight, welterweight and light-middleweight -- was seen as one of the few viable alternatives, despite his unimpressive draw against Sergio Mora in September.
Mosley has lost six of his 54 fights while 32-year-old Pacquiao, viewed by many as the best pound-for-pound boxer in the world, has only been beaten three times in his career and will be seeking his 14th consecutive victory.