Which running back should i start for my draft kings one week fantasy roster?

So for this weeks roster im stuck between starting bernard (bengals) or matin (tampa bay), both have been playing great so far and im not sure which one to start. I eould use them both but i already have one of spits filled with rawles (seattle). Right now im leaning towards martin because bernard shares his snaps with jeremy hill and wont be able to get much yards. But on the other gand bernard had a great game on monday and is facing a slacking rams defense while tampa bay is facing colts and im not really to sure how good their defense is (their team isnt one ive paid too much attetion to) any help/suggestions would be great