Former UFC champion Francis Ngannou is "crazy" for agreeing to switch to boxing for October's bout with Tyson Fury, according to unified middleweight champion Claressa Shields.

Ngannou, who relinquished his UFC Heavyweight title as part of his move to the Professional Fighters League (PFL) earlier this year, will make his professional boxing debut against the WBC Heavyweight champion in Riyadh, Saudi Arabia on October 28.

Fury's decision to face the unranked Ngannou has been criticised by many boxing fans after the Gypsy King failed to reach an agreement on a unification bout with Oleksandr Usyk earlier this year.

Shields made the opposite switch from boxing to mixed martial arts in 2021 and has a 1-1 PFL record, meaning she is well-versed in the differences between the disciplines. 

Ngannou will be a huge underdog when he steps into the ring for the first time, and while Shields is excited to see him in such a high-profile fight, she knows he is at a major disadvantage.

"It's going to be very interesting fight," Shields told Stats Perform. "Francis left UFC because of low pay. He wasn't being paid properly as a champion, which I felt terrible for – he had a couple of injuries and everything. 

"I think him coming to the PFL, they can offer him a nice cheque and really honour that he was a UFC champion and that he's going to work hard to be PFL champion. 

"I'm happy that Francis is getting his just [reward], fighting against Tyson Fury in boxing. I think he's just so crazy. 

"All the girls in MMA, I think, are very, very smart. If they were to come to box me inside the ring, I would destroy them, truth be told." 

Ngannou is, however, known for his punching power and is being trained for the bout by Mike Tyson, which Shields hopes may help the Cameroon-born fighter keep things interesting. 

"Francis has great hands, but in boxing and in MMA, distancing and everything is completely different," she added.

"I just feel like I just want to see it. I'm excited about it, and Francis is training with Mike Tyson, so we may see some things we weren't expecting to see. 

"I just know that Tyson Fury is a really great boxer. He's strong and I believe Tyson's going to win the fight, but I can't wait to see what Francis does to move from the cage."

Fury has previously discussed the idea of competing in MMA, but Shields is sceptical, adding: "I heard Tyson talking about it, but I don't think he would get inside the cage. 

"Inside the cage, under MMA rules, he gets kicked, [opponents] take you down to the ground and knee you and things like that. I just don't see Fury doing it. But he's crazy, so you never know."

Elsewhere, Anthony Joshua says "positive" talks have taken place over a heavyweight meeting with Deontay Wilder following the Brit's one-punch knockout of Robert Helenius earlier this month.

While Shields is fond of both fighters, she feels compelled to back fellow American Wilder if the bout is made.

"I am a fan of both," she said. "Deontay Wilder's like a big brother to me and Anthony Joshua's the heavyweight I have a crush on because he is so gorgeous! 

"But it has to be the American Deontay. Even though I think Joshua has better skill, I think Deontay Wilder has just got dynamite in both hands and we've seen Joshua get knocked out before. 

"I know I'm going to be cheering for Deontay Wilder, he's like my brother."