After announcing his retirement on Sunday, Conor took to Instagram where he posted a cake his family made for him reading "Happy Retirement Daddy."
Instead of sending his well-wishes, Floyd made his way into the comments to let the fighter know who's still the best.
"If I’m not mistaken, didn’t you tell Mike Tyson you could beat me if we fought a second time?" Mayweather wrote. "Now you’re quitting! I thought you wanted to beat the best? Well, if you decide to come back, I will be waiting to punish you again."
"Thank you Mike, and just know that for the inevitable rematch, with the knowledge I now hold of Floyd’s style, plus under the tutelage of my old school boxing coach, I will crack the puzzle, and I will beat Floyd," McGregor tweeted. "I promise my life on it."
Despite giving Tyson his word, Conor has decided to retire from fighting. He told ESPN he's "a bit bored of the game" and wants to find excitement in other areas of this life.