Knott and Klein made a lot of mistakes at first too, they were just masked by a decent DL. They had a little more time to react, last years LB's had no time to react. New players in any scheme don't fully know the system yet and can't just react without thinking.
The difference is Klein and Knott had the speed, strength, and athletic ability to recover from a mistake.
These "new players" you were talking about who played LB last year had mostly been in the system 3 years or more.