The 35-year-old, who originally wanted to go head to head with the Filipino fighter, is due to go up against Miguel Cotto for the Puerto Rican WBA light-middleweight title.
"We wanted the Pacquiao fight for May 5 but it didn't happen, so there's nothing I could do," said Mayweather. "You know, as I said before I'm always looking to give the fans what they want to see.
"I'm pretty sure Pacquiao has a tough task on his hands with the young fighter - I don't really know his name - but I've had a chance to watch him and he can box a little bit, so it's not going to be an easy task for him."
Mayweather will face Cotto in Las Vegas on May 5.