It's worth noting that Ellington touched the ball just 17 times during his spectacular 154-yard performance in Week 9 as the starter in place of Mendenhall. It's highly unlikely that number will increase when Mendenhall returns.
However, the "20 touches" comment by Arians underscores the Cardinals' realization that Ellington is their most dynamic running back. Even if Arians doesn't believe Ellington can be a between-the-tackles bell cow, the coach knows he needs to get the ball into his playmaker's hands.
It will be interesting to see if Ellington, a nonstarter, becomes a focal point of the offense or gets lost in the wash of Sunday's game.