Kevin-  I can't recall seeing Spillman or Robinson playing safety, so I'm not sure how good they are.  That would be a question for the coaches.  But you are right.  They may be able to step in and start if Goldson leaves.

In my opinion, Goldson and Whitner are the same kind of player.  Their skill set is better suited for playing strong safety.  The 49ers need a player who can better play free safety.