Her only dream, however, was to be the first female Olympic boxing champion. She had no aspirations to turn professional.
“When I first came on the scene people would say you do not fight like a girl, you fight like a man,” she says.
“But now that I’m a woman I say, I fight like a woman. A lot of these men wished they possessed the skills and the speed and the accuracy and the heart and the mindset as I do.”
At the world championships in China in 2012, just a few weeks before the London Olympics, Shields met Marshall for the first time. They fought in the preliminary rounds.
She lost and it remains the only defeat Shields has suffered as a boxer. But she went on to win two Olympic golds and as a pro become a 12-time world champion in three different weight classes and undisputed champion in two different weight classes at the same time.
“No man has ever done that. I don’t mean to brag but that’s the truth,” Shields adds.
Her long-awaited rematch with Marshall is being billed as the biggest fight in women’s boxing history.
A fight 10 years in the making with two women headlining an all-female card at the O2 Arena in London for the first time.
Shields has a chance to add yet another accolade and wipe out the only blemish on a career as remarkable as it is unprecedented.
“We can’t erase the loss in the amateurs because I don’t care about it,” she says.
“I don’t care what people say. That’s been a whole rise to greatness. They said becoming a two-time Olympic gold medallist was the hardest thing to do, it was impossible.
“People told me this but I did it. Beating Lomachenko’s record, becoming a three-time division world champion, impossible. I did it.
“There’s no way any fighter in history can become two-time undisputed champion, I did it. I don’t really care what they say.
“The only thing that matters is what I say and what I feel and I’m going to knock out Savannah Marshall.”