Savannah Marshall prepares for biggest fight of career against Claressa Shields, but then what?

Savannah Marshall (right) faces Claressa Shields (left) in an undisputed world middleweight title fight on Saturday. Mikey Williams/Top Rank Inc via Getty Images

Saturday's undisputed middleweight world title fight against Claressa Shields will be the biggest moment of Savannah Marshall's career -- and she admits she may never reach the same heights again.

The English boxer faces Shields for all four world titles at the O2 Arena in London (ESPN+, 2:30 p.m. ET), in what has been described as one of the biggest fights in the history of women's boxing.

But Marshall fears it could be a bittersweet moment for her.

After facing Shields -- win or lose -- WBO champion Marshall sees no potential fight to match it.

WBC, IBF, WBA champion Shields is already juggling boxing with a career in mixed martial arts (MMA) and the Michigan native is expected to return to the cage later this year for her third MMA outing.

While Shields (12-0, 2 KOs) has won world titles at welterweight and junior middleweight level, as well as middleweight, dropping down a weight class is not an option for Marshall (12-0, 10 KOs), who is 5-foot-11.

"I don't hate her, she just gets on my nerves a bit," Marshall, 31, told ESPN.

"Before I got the world title, who would want to box me when you have got a high percentage of getting knocked out? For instance, I spent three years trying to get hold of Ema Kozin.

"She didn't want anything to do with me but then took a fight with Claressa -- why? Because you could go 10 rounds with her and not get knocked out, coming out without a scratch [Shields beat Kozin by unanimous decision in February 2022]. But, if you box me, you have got a high chance of getting knocked out.

"After I beat Claressa Shields, there's no one else in this division and I can't go to junior middleweight, so I can only go higher to super middleweight and light heavyweight. There aren't the names in those divisions like the lighter weight divisions where you've got Katie Taylor, Natasha Jonas, Amanda Serrano, Mikaela Mayer and others.

"Maybe she's not getting what she wants from this sport, maybe she's not getting sponsorship or exposure like Katie Taylor is. Maybe she's not getting the sponsorship deals, endorsements and that's why she's doing MMA. But will she get the deals there? A leopard can't change its spots, she's finding hard to change her personality."

Perhaps Marshall's best option for a fight as big as Saturday's rescheduled clash -- it was postponed at late notice last month after the death of Queen Elizabeth II -- is a rematch further down the line. The rivalry is fierce between Marshall and Shields, established when the pair were amateurs, with Marshall having beaten the American on points in 2012.

"Deep down, there's definitely hate there from her," Marshall said. "I have given up trying to understand her, she contradicts herself all the time.

"My win over her [in 2012] bothers her. I'm quite level-headed but she's the opposite, really emotional."