Between the two I'd say Johnson will be phased in more and more as he gets comfortable. Robey-Coleman is not going to be any sort of long term answer in a starting role, which would include nickel duties.
Johnson has some really good plays on tape. I suspect he's one of those under the radar selections that will really pan out for us but probably not right away.
And I'm not concerned with the safety position, as I do like Mo Alexander a lot. I think Wade will have enough talent there with him and Joyner, it's CB that is potentially the issue so again hopefully we have a fierce pass rush.