Bruce Arians: David Johnson 'the lead guy' in Cardinals backfield

With running back Chris Johnson out for the regular season, the Arizona Cardinals will rely on rookie David Johnson to carry the load in his absence.

Despite the presence of Andre Ellington - who head coach Bruce Arians is optimistic will play Sunday against the St. Louis Rams - Johnson is being characterized as the go-to back.

"He's the lead guy now," Arians told SiriusXM Radio, calling Johnson "more than ready."

Coming into the season, Ellington was the bell cow of the Cardinals running game - though his slight build and injury-prone history necessitated drafting the bulkier Johnson.

Now it appears Ellington will continue in a change of pace role when he returns to full health.

The Cardinals also added Kerwynn Williams off their practice squad as they continue to battle through injuries at running back.