The college LB to S move has been done successfully a few times.

 

The two that leap to mind are:

 

Carnell Lake, who played OLB at UCLA before moving to S with the Steelers.

 

Darren Woodson made the move from Arizona St LB to S with Dallas.

 

But both played SS, not FS.

 

Conceptually it's possible, but if Smith were to make the move, most likely it would be to SS.

 

To me that would be a waste, considering Cyprien is already back there.

 

Keep him at LB.  He already understands the position.  It's just a matter of him putting on weight and getting stronger, as opposed to learning an entirely new position.

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