At this point Revis and Lowery are the starting cornerbacks. Poteat is the nickleback and Drew Coleman is the fourth. Barrett will probably wind up being the 3rd or 4th safety and 5th cornerback. I don't know what they are going to do with Justin Miller. He is not a good cornerback and he can't stay on the field.
He doesn't have to be outstanding, though that would be nice, he will be the number two, and just have to be solid coverage and a sure tackler. JMO.