Floyd Mayweather has told Khabib Nurmagomedov: Show me the money!
The UFC lightweight champion called out the boxing legend for a fight after his win over Conor McGregor.
Mayweather, who stopped the Irishman in the 10th round last summer, said: "CBS, Showtime and MGM Grand get the checkbook out!"
Nurmagomedov submitted McGregor at UFC 229 earlier this month as he retained his belt and preserved his unbeaten record.
The Dagestani said: "Hey let’s go Floyd, we have to fight now.
"50 and 0 versus 27 and 0, two guys that never lose. Let’s go, why not. Because in the jungle only one king, only one king.
"Of course I am the king. Because he [Mayweather] can not drop McGregor but I drop him easily."
Mayweather, who has not fought since he defeated McGregor to move to 50-0 as a professional has been critical of Nurmagomedov's role in the riot that followed his win over the Irishman.
He said "I'm not too familiar with the guy McGregor was fighting, but I know the guy he was facing was undefeated.
"McGregor is a tough competitor but McGregor's opponent jumped out of the ring and was fighting people in the crowd so, very unprofessional.
“It's going to be a huge fine I'm pretty sure because with my fight against Zab Judah, there was a crazy melee in the ring and a huge penalty - a huge fine. If I'm not mistaken, seven figures.
"Not to me, but could have been to Zab Judah or my uncle Roger or even Leonard Ellerbe, so I know when a guy's jumping out of the cage into the audience and fighting different people, the fine is going to be crazy.”
Mayweather is expected to fight long-time rival Manny Pacquiao for a second time next spring.