No one expects a 4th OF to be perfect. In fact, just one above average skill can make someone a useful bench player. If Carrera were a good base runner or could hit a little or fielded well there would be a way to put that single skill to good use but he literally does nothing well. Heck if Ceciliani were merely slightly below average at all those things but not flat out terrible at anything, he'd probably still be an improvement.