Your making it sound dire than what it is. We actually need only 1 CB with Melvin White playing good as he did for a undrafted rookie. He has the size and to play outside and with a season under his belt he should improve significantly. We have Captain to play the slot that leaves us to draft 1CB to play opposite of White. We also have a good combo at SS & FS with Mitchell and Lester. The WR situation isn't bad since we can address it with the deep class of WR in this year draft. We have Smith to play slot and resign GInn & Hixon for depth. We can draft a WR from rounds 1-3 that would be a starter (Allen is a 3rd round pick for Chargers) Benjamin, Mathews, OBJ, Moncrief, ..... We can pick a solid run blocking TE like Arthur Lynch in the 4th round while addressing OT with either 1-3 round picks and use FA to pick up a LT.
None of our CBs are starting material.