Stafford doesn't make decisions on player personnel lol
I'm sure they take his input and his considerations. I think I remember in an interview him saying essentially what I did, which is why I mentioned it. He prefers having someone with experience to breakdown film and give him pointers since he doesn't have time to watch everything.
Obviously he doesn't have final say, but I think you are fooling yourself if you don't believe that had something to do with the decision.
I'm sure the other part was that Rudock is practice squad eligible while Cassel obviously is not, So if you can keep both, why not. But I have no doubt Stafford would prefer to have Cassel on the sideline of games instead of Rudock.