There's no question who the third greatest running back in Steelers history is
Le'Veon Bell did it all. An outstanding runner who may have better receiving ability than taking it out of the backfield. He's a do-it-all runner, and because of it, he's earned his respect.
Don't get it wrong, Willie Parker did remarkable things. He's engraved himself in Steelers history, but his short-lived NFL spark isn't enough to compete with Bell's start in Pittsburgh.
Leaving the question with a simple answer - Le'Veon Bell is the third-greatest running back in Steelers history. Franco Harris and Jerome Bettis reign one and two. And Le'Veon Bell made his way right behind them.