Depth, the #4 CB, plays a lot. I'd all that position backup, and the others depth.
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In any case, Macus Jones has shown nothing to make me believe that he should be our starter at nickel back. Both Bryant and Wade are ahead of him at nickel. For me, Marcus is our #5 CB, which is a fine position, given that he is one of the best punt returners in the NFL.
STARTERS (need 3): Gonzo, Jonathan, ???
COMPETING FOR #4 CB and #6 CB: Bryant, Wade, Austin, Bolden, Wilson
PUNT RETURNER and #5 CB
Perhaps the staff has judged a couple of the backups as being a starter. Personally, I'd be more comfortable with signing a free agent CB (and free safety).