Conor McGregor heard about Floyd Mayweather Jr.'s First Take appearance and fired back on Twitter, sending out a tweet referencing the boxing star's history of domestic violence Wednesday:

Text messages from NBA guard C.J. Watson reportedly upset Mayweather before his 2010 assault of Josie Harris, Mayweather's girlfriend at the time and mother of three of his children. Mayweather was sentenced to 90 days in jail for the assault, his latest conviction stemming from a series of domestic violence accusations over the last decade-plus.

During his appearance on First Take, Mayweather touched on his negotiations with McGregor regarding a potential megafight that would bring the former out of retirement. The 39-year-old has not fought since a September 2015 win over Andre Berto.

McGregor, the most popular name in mixed martial arts, has never boxed professionally. He became the UFC's lightweight champion after defeating Eddie Alvarez at UFC 205 in November. That win allowed McGregor, who is also the featherweight champion, to become the first fighter in UFC history to hold two titles at the same time.

On Wednesday's First Take program, Mayweather called McGregor out. 

"You guys keep hearing all these different rumors about different fighters want to face Floyd Mayweather," he said. "Everybody keeps talking about Conor McGregor. He's blowing smoke up everybody's ass. Dana White, the UFC—let's make it happen. Bring him over to the boxing world, and I'll show him what it's like."

Mayweather has consistently said his price tag for a return is $100 million guaranteed. McGregor has said he wants the same—a notion Mayweather scoffed at during his ESPN appearance.

"We are willing to give him $15 million, and then we can talk about splitting the percentage—the back end—on the pay-per-view. But of course, we're the 'A side.' How can a guy talk about making 20 or 30 million if he has never made 8 or 9 million in a fight."

With an $85 million difference in opinion, the odds of the fight ever taking place are slim, as they always were. McGregor would be taking a massive risk by leaving MMA and stepping into a boxing ring against the best pound-for-pound fighter of his generation. He would be an overwhelming underdog, more likely to be embarrassed than pull off a major upset.

Mayweather, ever the opportunist, sees this as an easy $100 million to put in his back pocket. But there's an inherent risk that McGregor finds an opening for one punch and reshapes the 49-0 Mayweather's legacy forever.

The overwhelming likelihood is that this plays out like Mayweather-Pacquiao without the payoff. Every couple of months, McGregor or Mayweather will likely say something inflammatory to spark interest, but the downside is too great for both parties.

Follow Tyler Conway (@jtylerconway) on Twitter.