Manny Pacquiao wants to become the first fighter to defeat Floyd Mayweather Jr, but the Filipino boxing icon admitted that Amir Khan could be the first one to put a blemish on the undefeated American's record.

Pacquiao, who has been pushing for a blockbuster showdown with Mayweather, told BoxingScene that Khan is more than capable of defeating the reigning pound-for-pound king.

The 25-year-old Filipino is familiar with Khan's fighting style and skills having spent a lot of time together in training at the Wild Card Gym and in the Philippines when the British boxing icon was still under the tutelage of Hall of Fame trainer Freddie Roach.

Pacquiao said that Khan, who now trains under Virgil Hunter, has the style and speed to put Mayweather in trouble. But he added that Khan should learn how to use it to his advantage and train very hard in order to have a chance against the 36-year-old American.

"Amir Khan, it depends on how hard he trains. He has a chance because he has speed. That's good for him," Pacquiao said.

Several boxing analysts have been questioning whether or not Khan's chin could take the punching power of Mayweather, who knocked out opponents in 26 of his 45 victories.

In his previous fights, Khan struggled to take punches, which led to devastating knockout defeats against Breidis Prescott and Danny Garcia. Khan also went down in the fourth round of his showdown with Julio Diaz in April last year.

When asked about the vulnerability of Khan's chin, Pacquiao said that Khan could improve that aspect as long as he trains hard for his possible showdown with Mayweather.

The former pound-for-pound king admitted that his chin was not one of his greatest assets as was proven by his knockout losses to compatriot Rustico Torrecampo in 1996, Medgoen Singsurat in 1999, and most recently against Juan Manuel Marquez in their fourth showdown in December 2012.

"If you look at the problem of the chin, I had that before, early in my career, and I developed a better chin," Pacquiao said. "He needs to train hard if that fight happens. He has a chance."

Mayweather has yet to announce his opponent for his next bout on May 3 in Las Vegas, but the Grand Rapids native is expected to pick Khan, who edged Marcos Maidana in a poll conducted by Mayweather.