I am not sure what you mean by rotation guy, but Gregory will be the starter and he will be on the field as much as they can get him out there assuming he doesn't fall of the wagon. The guys was the most disruptive guy on that defense when he played last year.
The problem is after him there is nothing else, unless you want Dorance Armstrong to be the backup - which I don't think is good enough. If they can sign Smith for a decent price they would be wise to do it.
Anae is a rotation guy, but he couldn't crack the lineup last year so we have no idea if he is a piece of the puzzle yet.