Claressa Shields is not concerned with Savannah Marshall exercising a rematch clause in the aftermath of their upcoming fight.

Shields, who holds the IBF, WBA, WBC middleweight titles, will collide with WBO titleholder Marshall in an undisputed showdown on September 10 at the O2 Arena in London.

The two have had a rivalry for several years - which stems from Marshall winning a decision over Shields in the amateurs.

As an amateur, Shields would move forward to win gold at two Olympic games. In the pros, she also became a three division champion, with undisputed runs at middleweight and junior middleweight.

The amateur loss to Marshall is the only blemish suffered by Shields in the squared circle.

Some oddsmakers have listed Marshall as a slight favorite to win the fight. She holds the big advantage in power, while Shields is viewed as the quicker and more technical fighter.

During a recent interview, Shields revealed that both her and Marshall have the ability to exercise the option for an immediate rematch.

Shields is predicting a win so dominant that Marshall will be reluctant to have a second encounter.

"There's a rematch in the contract, it's there," Shields told Sportsmail. "We can both activate it after the fight. 

"I'm not worried about it; we had a rematch clause when I fought against Christina Hammer. She never activated it. It is what it is. It's going to be her losing, because I'm not going to lose. You can note that, and everybody can ask if or when or how. I'm going to win by any means necessary. Period."

Shields won a lopsided decision over Ema Kozin back in February. Marshall picked up a brutal three round stoppage of Femke Hermans in April.