I'm a little confused by SS FS CB. They all have the same abilities and I signed a "CB" to find him a "FS" on my team. Is there a reason to switch a player from FS to CB? What are the criteria to assign them in the depth chart? The fastest as CBs, the most intelligent as FS and the strongest as SS? Thanks!

There is some degree where you can move between the various defensive backs, your CB's will need to be faster and be your better man coverage guys, your safeties will be making more tackles in the run game, especially the strong safety. The FS will spend a lot of time in zone coverage. Of course, it does vary depending on your playbook, if you look at the play cards you can see what each position's assignment is to get a feel for it.

The passing game matchups have been something I've been meaning to ask about for a while now. Guess this is as good a time as any.

Are there certain receiver attributes that make it easier for them to get open vs zone coverage? Is there, for example, a WR attribute that is ever compared against a DBs zone coverage rating?

Route running vs. man-to-man comes more into play on man-to-man coverage, and as a receiver enters a zone the defender will play a measure of man-to-man while he's in the zone, depending on how close the receiver is to the center of the zone. The defender's zone coverage skill basically determines how well he stays in his zone, i.e. he may follow a player through his zone and his "zone" may move as he loses track of where he's supposed to be. The other comparison is courage vs. punish receiver which comes into play when the DB is on a collision course with the receiver.