From Josh Katzenstein on NOLA.com:
Maybe he “graded” poorly as an OLB because he was really an MLB?
Linebacker A.J. Klein joined the New Orleans Saints in March, hoping for a chance to start and help turn around a defense that had struggled the previous three seasons.
He quickly ingratiated himself with the team this year, earning a starting role and becoming a captain, and Klein was among a handful of new players that helped the Saints play a consistently better brand of defensive football this year.
...
Replacing Klein won't be easy because of his versatile role. He was the starting strong-side linebacker in the base 4-3 defense, but he played mostly in the middle because the defense relies most of packages with just two linebackers.
Maybe he “graded” poorly as an OLB because he was really an MLB?