First off, Aaron Ross' hamstring injury is severe enough that he won't play Sunday. Second-year corner Terrell Thomas has already been told he's been starting. That means he's jumping over Kevin Dockery, who may also sit because of a troublesome hamstring that kept both he and Ross out of practice yesterday.
Ross didn't play at all in the preseason, so the Giants are definitely going to go slow with him. And Tom Coughlin said they'd be cautious with Dockery, too, which means University of Miami rookie Bruce Johnson could see significant time at nickelback.
That should be cause for worry, although Thomas is not a bad player by any stretch. But Dockery has proven his worth over the last couple of years, while Thomas is still developing. Ideally, the Giants would be better off with Dockery in there. But, like defensive tackle Chris Canty, it might be worth it for the Giants to sit Dockery a game or two and make sure they have a healthy starter/nickelback for a good stretch of the season.
We'll talk more about that situation as the week progresses.