Savannah Marshall and Claressa Shields have known each other a long time.

Ten years on, they have become bitter rivals and two world champions at the peak of their powers.

When Shields, now 27, enters a room already occupied by Marshall, tensions rise. The pair are often kept apart, ushered into events at different times, meeting briefly for a face-off that usually ends in a shouting match.

It’s a rivalry unlikely to be put to bed on Saturday night, but how did it all begin? Why has it gone on so long? Is it a real feud or hyped up for the cameras?

First meeting in China

The rivals first met at the 2012 AIBA world championships in China in May 2012.

“I remember when I got there everyone was talking about this young American that had never been beat. She was the next superstar,” Marshall recalls.

Marshall, now 31, was preparing for the London Olympics while Shields was chasing qualification. It was only the second international tournament Shields had competed in and she was fresh off a shock win against three-time world champion Mary Spencer at the continental championships that summer.

Shields saw Marshall before they were drawn to fight each other. “Her coach was looking at me,” she remembers.

The two women faced off in a fight that has gone down in women’s boxing folklore. Marshall emerged the victor on points, 14-8. She says she won easily, Shields believes she edged it.

Mikaela Mayer, a current world champion and a USA team-mate of Shields at the time, remembers the encounter.

“I remember Savannah boxing and moving and keeping that perfect space away from Claressa,” she says. “Not letting her close that space and letting her hands ago. The fight got away from her in those three rounds.”

Marshall believes that defeat, the only loss of Shields’ entire fighting career to date, “eats” away at her. Marshall won the world championships a few days later, Shields the London Olympics in August. This was the foundations of their rivalry.

“We can’t erase the loss in the amateurs because I don’t care about it,” Shields says.

“I’m going to show everybody I was better than her then and I’m better than her now,”

Sparring stories & different amateur paths

Four years after their first meeting, Marshall travelled with Team GB to Colorado for a two-week training camp in preparation for the Rio Olympics.

Marshall and Shields were the only two female middleweights. Shields was the reigning Olympic champion.

But it wasn’t until the last day of the camp that they sparred together.

“Nothing happened,” Marshall insists.

Shields, of course, has a different version of events, saying: “I pulverised her for four rounds.”

The rivals’ amateur careers played out very differently. While Shields became a two-time Olympic champion in Rio, winning every amateur championship she entered, Marshall stumbled repeatedly.

She was knocked out of her home Olympics in London in the preliminary rounds and would suffer a similar fate at Rio 2016. As Shields excelled, Marshall considered walking away from the sport altogether before a certain American superstar changed her mind.

Rivalry repackaged for the pro game

Fast forward to 2016 and Shields has turned pro. Marshall followed her into the paid ranks a year later.

Marshall was snapped up by Mayweather Promotions after seriously considering retiring. But the lure of a burgeoning pro game and the backing of all-time great Floyd Mayweather was too much to turn down.

And a big part of the interest in Marshall was her history with Shields. An opportunity to repackage the rivalry for the pro game.

But Marshall struggled for exposure under Mayweather in America and would eventually sign with Eddie Hearn’s Matchroom in 2019. Meanwhile, Shields had already won world titles in two weights and had just become the undisputed middleweight champion.

Hearn immediately set about hyping a rematch. Shields was unbeaten in the pros, as was Marshall, and it seemed inevitable the pair would meet again.

Timing was off, as it often is in boxing, and it would not be until 2021 when Marshall linked up with promoter Ben Shalom and Boxxer that the promises of a rematch finally materialised.

Shields was immediately signed to a two-fight deal with Boxxer and broadcaster Sky Sports. She fought in the UK as a pro for the first time in February, comfortably beating Ema Kozin on points.

She watched from ringside as Marshall defended her WBO title with a destructive third-round stoppage victory over Femke Hermans in April.

“I was dominant in the amateurs. I lost one time,” Shields says. “There was never a rivalry. That’s what is said but it’s not true.

“In the pros, if you want to live off the amateurs you can. I don’t live there. I turned pro.

“I’m the only boxer who is two-time undisputed champ. No man has ever done that.

“I don’t mean to brag but that’s the truth. She’s sold everyone this story that she beat me up so bad in the amateurs. She’s better than me. I only got to the belts before her. All this mess and everybody believed this.”

It was an easy fight to make, according to Shalom, such was the rapidly rising interest in the women’s game.

After a delay in the summer and then a postponement from 10 September to 15 October, the stage was finally set for two of the best in the women’s game to go toe-to-toe.

‘We clash massively’ – Opposites attract and collide

Ultimately, Shields and Marshall are very different people. While they share a sense of hard work and loyalty, their personalities could not be more different.

Shields is outspoken, oozes supreme confidence and probably would not shy away from a verbal altercation with the Pope, were he to question her fighting abilities.

Marshall is the opposite, struggling with shyness throughout her career, only recently has her quiet confidence emerged.

“We clash massively. I’ve known Claressa a long, long time. I’ve given up trying to crack that code,” Marshall admits.

“The things she comes out with, she’s either not wired right or she’s trying to play the baddie.”

Shields and Marshall have had a few verbal altercations. One that stood out was after Shields’ most recent win. The American erupted as Marshall taunted her, pretending to fall asleep at ringside in Cardiff.

Insults flew between the two and that energy has carried through until fight night. They have argued on Twitter, mocked each other from afar and even imitated one another at press conferences.

On Saturday their differences will be settled in the ring. A close fight could ignite the potential of a rematch and even a trilogy. The rivalry is unlikely to end under the lights on fight night.

“I’m not here to be friends with her. I’m here to fight for a world championship. I’ve trained so my confidence is [huge]. The work I’ve put in and knowing she hasn’t, it’s going to be popping,” Shields adds.

“It’s all a bravado,” Marshall says. “She’s here because of me. She’s here because she can’t sell a ticket. I mean you could ask the average person on the street who Claressa Shields is? And really her face should be on cereal boxes.

“Of course I do, I respect Claressa. Not just as an opponent, but what she’s done for the sport. She rubs people up the wrong way, but she’s undisputed champion.

“I’m not stupid. I know what she’s about, I know what she’s done. That can’t be overlooked.”