Marshall is eager to make sporting history by facing Shields again in MMA and would relish the chance to "choke her out" if they were to meet in the Professional Fighters League.
Marshall, the undisputed super-middleweight world champion, signed a multi-year contract with the mixed martial arts promotion.
She will now be competing against her longtime rival Shields, who she defeated as an amateur but lost to by unanimous decision in October 2022.
Marshall believes a rematch with Shields in boxing is very unlikely, but she predicts that a fight in the cage would be even bigger than their previous contest.
“The opportunity I was presented to by PFL (Professional Fighters League) was amazing and something that I really couldn’t walk away from,” Marshall told the PA news agency.
“The PFL have been interested in me since my fight with Shields last October and working alongside my manager we managed to get something over the line.
“Yes definitely (Shields was the motivation to sign for PFL), I don’t think I get the rematch in the ring and it’s more likely that I get it in the cage, and so that added to the decision making.
“I’m naturally stronger and we’re both in the same position even though she’s had two fights in the cage – Shields beat Brittney Elkin before losing to Abby Montes.
“But I think I beat her, I really do and, for me, she beat me in the ring so I have a chance to even it in the cage and this is not something that has been done in sport before.
“It would be unbelievable, it would be huge. I think the first fight was huge and this would be even bigger.
“I would definitely make it 1-1. I’d relish in just choking her out and squeezing the breath out of her.”
Marshall’s majority decision victory over Franchon Crews-Dezurn in July saw her crowned super middleweight queen – she now holds the WBC, WBA, WBO and IBF belts. And the Hartlepool fighter, who also won The Ring championship against Crews-Dezurn, admitted the loss against Shields motivated her to claim victory last month despite considering quitting the sport last year.
“I’ve learnt a lot about myself after that fight I was ready to walk away and it really hurt me losing that fight,” Marshall added. “But I came back and beat Franchon to become undisputed champion so it goes to show that when the going gets tough, especially at that level, there’s always something around the corner where the hard work pays off.
“It feels amazing to be an undisputed boxer and it’s a surreal feeling to have all five belts, and it’s amazing knowing that I’ve had my name cemented in history.
“I feel fulfilled in myself knowing how far I’ve come and my path could have took a different turn at any given point in my career.”
Shields was ringside for Marshall’s last fight and was vocal throughout the night.
Marshall said: “Claressa is just Claressa and I don’t think she did herself any favours at all, and the way she went on at ringside was just embarrassing. I don’t think she helped herself there.
“She’s not my type of person and our personalities clash a lot.
“This rivalry has been going on now for over 10 years and she’s just not my cup of tea.”
