Marshall has been buoyed by the fact she became the first fighter to stop Rankin, while Shields landed a points win over the game Scot in 2018.
The American – who won Olympic gold in 2012 and 2016 – has tweeted screenshots of text message conversations with her mother, who states Marshall “deserves” to be on the end of “a knockout”.
Marshall’s trainer Peter Fury – who guided Tyson Fury to the world heavyweight title in 2015 – told the 5 Live Boxing podcast: “Shields is a very good fighter and deserves to be where she is.
“I believe not only does Marshall have her number, she’s inside her head and it will be a major problem when they do meet because Shields has totally read the script all over the place.
“Savannah is the new talent in world middleweight boxing, not Shields. Everyone in the country wants to get behind her as we have a new superstar in boxing.”
Marshall’s world-title success and eye-catching spat with Shields has drawn interest in women’s boxing just days before Ireland’s Katie Taylor headlines a card where the three biggest fights are all contested by women.
Taylor – the undisputed women’s lightweight champion – has unquestionably elevated the sport, as has Shields in her four years as a professional.
“We have great women boxers like Katie Taylor doing fantastic stuff,” added Fury. “Women’s boxing is going to fly. I think within two years women’s boxing will be almost, if not nearly there, on the same base level as men. It’s getting there very fast.”