COOK vs Mattison problem

I Have CMC and COOK as starting running backs
In my FLEX is MILES SANDERS.
if cook plays should I bench sanders and put in MATTISON? OBVIOUSLY putting in Mattison if COOK is out.

BENCH PATRIOTS D?
For Packers D this week?

If Cook plays, you should not play Mattison if you have Sanders. He is in a bellcow role with them the last few weeks and Howard is still not cleared for any contact. He is also playing the giants. Mattison is too much of a mystery if Cook is on track to play.