Boxing champion and MMA star Claressa Shields has elaborated on her comments about Jake Paul, a celebrity boxer with 20 million YouTube subscribers.Speaking at a Professional Fighter League press conference last week, Shields refused to fight on the undercard of Paul.She also claimed she would "beat him up" if the pair met in the ring."Don't ever disrespect me," she said in September. "I would never fight on the undercard of Jake Paul. I'm a three-division world champion and a two-time Olympic gold medalist in boxing.""I could beat up Jake Paul at the weight class I'm at right now," the American continued. "I would never fight on the undercard of someone who does not possess the skills or accomplishments that I have."With her second MMA fight set to take place at a PFL Championship event tomorrow, Shields has now elaborated on her words."What has Jake Paul done that’s so great to where he gets to be the main event pay-per-view on Showtime, but I don’t?" Shields said. "I gotta fight under him. That’s the thing, it’s like I actually earned my opportunity."They’re just giving it to him. They’re like, 'Hey, you’re Jake Paul, you’ve got a million subscribers on YouTube, you and your brother get to fight main event on Showtime."That’s trash. I literally earned my spot and never was given an opportunity. That’s what pisses me off. It’s not really Jake Paul, it’s more like how dare they give him the opportunity that I earned."

Shields added: "I fought the main event on Showtime six times, sold out arenas for Showtime, and still would get the ‘We don’t think you’re big enough to fight on pay-per-view.’ Get out of here. It’s crap.

"That’s why I would never fight on the undercard of him or nobody else who haven’t earned it.

"If they’re not a world champion, Errol Spence, Manny Pacquiao, Floyd Mayweather, Terence Crawford, even Shakur Stevenson, if they not under them I’m not fighting on no undercard of no other men."

Shields is set to take on Mexico’s Abigail Montes tomorrow, having defeated Brittney Elkin in her first MMA fight in June.

The 26-year-old Shields is the only boxer in history, female or male, to hold all four major world titles in boxing, simultaneously, in two weight classes.

She is also a double Olympic gold medallist, having triumphed at London 2012 and Rio 2016.