Youtube star turned boxer, Jake Paul, has fired back at unified two-division world champion Claressa Shields - after the two-time Olympic gold medal winner suffered a split decision loss in her second MMA fight on Wednesday night.

Paul manages the career of another unified female world champion, Amanda Serrano.

Over the last twelve months, Shields has shot off plenty of harsh words in the direction of Paul.

In a recent interview, Shields told reporters that she could beat Paul with one hand tied behind her back.

“Jake Paul? Please. Look, there are a lot of women in boxing that can beat up men, especially an average Joe like Jake Paul. If I was to spar Jake, which is all I would get because a real fight would be too embarrassing, right? But if we were to spar, I would use one hand — not even the banger, I’d use my jab and I could out-jab and hook and uppercut him and embarrass him. That’s how skilled I am. It’s not a shot at Jake, but he’s not as good a boxer as me," Shields said.

“I’ve sparred against those guys too — Olympic gold medalists, silver medalists. I’ve sparred against all of them. Those guys would destroy Jake just like I would. I box for real, not play stuff. I box for real.”

Paul fires right back, with a big congrats to Shields' conqueror, Abigail Montes.

“The truth hurts but it’s necessary. Claressa Shields is a loser. In MMA, and even more so with her prima donna attitude. The fake always get exposed. Losses come when anger and hate take over. Just ask (Ronda) Rousey and (Conor) McGregor. She spent more time berating Jake Paul than learning Jiu Jitsu,” Paul wrote on social media.

“(Shields has) never been a big draw and unfortunately for her she never will be. Amanda Serrano (the GWOAT), though, has 30 KOs in 42 fights. 2-0 in MMA, both wins by submission. Congrats Abigail Montes on the win.”

Shields is scheduled to defend her IBF, WBC, WBA middleweight titles on December 11 in the UK, in a mandatory fight with Ema Kozin. If she wins, a grudge match unification with WBO champion Savannah Marshall is on deck for 2022.