Martin may not be available to play and Fred might not suit up either.
If both of them are out it wont be much of a "dress rehearsal" for the starting offense. I cant imagine the coaches letting Prescott and Elliott play much in a preseason game if those two are both out. They both might start, but rather than play the entire half or into the 2nd half, they might only see a series or two.
That's probably going to be the case against Carolina.