Patterson is in no way shape or form competing with Barber for a roster spot.
You are not getting a sub 200lb back to be your short yardage guy, and that is the role Barber provides, and a role he is pretty good at.
Patterson's main competition for touches is Gibby, McK and Samuel, not Barber.
The day you consistently send Patterson into the nature and number of looks given to Barber is the day Patterson dies. 195lb guys don't do that and stay healthy in today's NFL.