After Monday’s surprise announcement that Floyd Mayweather would participate in a bout with kickboxing prodigy Tenshin Nasukawa on Dec. 31 in a vaguely defined exhibition bout in Japan at RIZIN 14, you knew it wouldn’t take long for Conor McGregor would respond.

McGregor, after all, was the undefeated boxing superstar’s first crossover opponent, losing via 10th-round TKO in an Aug. 2017 boxing match which did blockbuster business.

And indeed, “The Notorious” chimed in on Monday with an expletive-riddled post on Instagram, taunting his former opponent.

“Is that a tracksuit or a sauna suit Floyd haha wtf,” the post read. “Is it hot in Tokyo or what’s the story here? That climate change is no joke f*ck me hahah. What in the f*ck is going on here? Who’s this little prick next to you ? That’s mad sh*t. Like something out of rush hour 5 or something. Chris tucker and Jackie f*cking Chan back in this b*tch. F*cking brilliant. Mad little bastard you are Floyd. Fair f*cks to you mate. No lie. F*ck it.

Few details were provided by RIZIN on the rules or length of the fight for the Dec. 31 card, nor was a weight class specified. Mayweather is 50-0 as a boxer, while Nasukawa is 27-0 in kickboxing and 4-0 in MMA.

McGregor, the former UFC lightweight and featherweight champion, is coming off his fourth-round submission loss to Khabib Nurmagomedov at UFC 229.