Mayweather Jr. and Pacquiao look to be on the verge of fighting each other on May 2 at the MGM Grand in Las Vegas in a much anticipated clash.
The British boxer has trying to secure fights with both men but for now neither fighter has shown any interest in facing Khan yet.
Khan is picking Mayweather to struggle early, then adjust, and outbox Pacquiao to a twelve round decision win.
"You never know, Mayweather might get old overnight. He's shown he's getting caught more so he's not invincible.
“Pacquiao had speed, explosiveness and power so I think he will give him a lot of problems early but I think Mayweather will just move on and drift away by picking him off with clean shots and frustrate him," Khan told Daily Mail.
"I think it will go the distance but that Mayweather will win by unanimous decision. Four years ago it would have been a massive fight because both of them were at their peak. It might have gone past that now and it's not going to be what people expect," he added.