“Kamaru Usman, I respect you, you were one of the best, but now you are old, bro, and you know that my time has come!” Borz wrote on the social network, referring to the former UFC champion.
Both fighters had previously expressed interest in fighting each other, however, UFC president Dana White was less than enthusiastic about the idea, stating that the fight could only take place in the middleweight division.
Kamaru Usman, 36, is on a two-lose streak against Leon Edwards in title fights, while Khamzat Chimaev, 29, won his sixth straight UFC win last September, defeating Kevin Holland in the first round.
Currently, Usman and Chimaev occupy the first and fourth lines in the UFC welterweight rankings, respectively.