Pacquiao, 40, won raves from boxing fans when he beat the previously undefeated Keith Thurman in an exciting WBA welterweight title bout last Saturday night, improving his record to 67-7-2.
The retired Mayweather, 42, saw it live at Las Vegas' MGM Grand Garden Arena. But instead of congratulating Pacquiao on his age-defying performance, "Money" shared a stinging critique of his former rival's legacy on Instagram.
"I find it real ironic how every time Pacquiao's name is brought up in the media, my name is always attached to it. This man's entire legacy and career has been built off its association with my name and it's about time you all stop using my brand for clout chasing and clickbait and let that man's name hold weight of its own."
Mayweather continued, "For years, all you heard was that 'Floyd is afraid of Manny Pacquiao.' But what's funny is, when we finally fought, I won so easily that everyone had to eat their words!
"All of the so called boxing experts, critics and jealous American 'fan base' either went mute and ran for cover or made every excuse in the world as to why I should give Manny Pacquiao a rematch."
Forbes notes that the Mayweather's analysis of Pacquiao's career is "ridiculous," as Pac-Man is still the only eight-division champion in boxing history. But Mayweather didn't exactly shoot down the idea of a rematch, so Pacquiao went ahead and dropped a "#MayPac2" hashtag on Twitter.
"You come to my fight and then use my name in a post but I’m the one that is trying to stay relevant? If you want to be relevant again...#MayPac2," Pacquiao wrote.
Mayweather fired back in a second Instagram post.
"Bottom line, I make more money than you; I beat you, then I signed you!" he wrote in reference to the fact that Pacquiao's promoter, PBC, and Mayweather Promotions fall under the same umbrella, according to USA Today.
"I was only at your fight supervising you, my employee, as any real BOSS would do."
Pacquiao challenged Mayweather's claims.
"Excuse me Floyd, your name has not been on any of my PBC contracts," he wrote. "But if you would like to be on the next one, I will have one drawn up and sent to you. #CounterfeitMoney."
The last time these two were in the ring, Mayweather won by unanimous decision in a hotly-anticipated fight that racked up a record 4.6 million pay-per-view buys but was panned by the vast majority of boxing fans as a disappointing snoozefest.
Would you watch Mayweather vs. Pacquiao II?