I'm not buying the fumbling bit - there's got to be other issues going on behind the scenes. He's got 9 career total fumbles in a little over three full seasons, three this year in limited action. Adrian Peterson had 20 his first three years in the league.
EVERY running back who played deserved to be inactive after the Cleveland game based on their performance. I'm more concerned about Tomlin fumbling his coaching duties more than Mendenhall fumbling the ball at this point.