With a 53 man roster (46 active on game day) it is virtually impossible to completely rest most of your starters (33 or more total including special teams). For example, when you are only carrying eight offensive linemen at the very least two regular starters will have to play at least most of the game, if not all. You may be able to sit Thomas and Kamara, but the rest will be forced into playing far more snaps than normal. Also, take into mind, that with so many backups in play there is a far greater chance that one of the normal starters that has to be on the field will suffer an injury. Missed blocks and missteps could cause rolled ankles and such.

It's a bit of a double edged sword.