Who should I start at the FLEX

I have a matchup this week in a standard scoring league and I can’t decide to use as my flex. As of now I have Gillislee and Bell as my starting RBs. D. Parker and Diggs at the WR. And for flex options I have Martavias Bryant, Kupp, Marvin Jones and Javorius Allen.

M.Bryant’s ceiling is miles higher then the rest.

Start Bryant

Thanks for the advice