I am not a big fan of Chris Johnson this year, but he would be your #3 RB. He has more upside than Ridley, but Ridley will be much more consistent, so that is up to you if you want consistancy or the Chris Johnson headache with upside.
I think Marshall is an upgrade at WR for Dez. I do not see him breaking out this year. He will have an ok year, just not huge. With this not being a PPR league though it is not a huge upgrade. I think Marshall has a hard time catching the ball in the endzone and will not have double digit TDs. He should have 1200 yards though.
Hope this helps, sorry I could not choose one way or another,
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