He had that torn acl his last year at college which was probably the most pain he's ever felt in his life he may be playing more timid because of that.
He is several years removed from that. I highly doubt you can point to his health as a problem.
In 2012, he looked extremely comfortable in the 3-4 filling in for Lee inside. He was practically dominant at times and had everyone talking about him being part of the future, right along with Bryant, Lee and Smith. He was part of the "when should we lock him up" discussion.
From what he did last year, he suddenly looked like a casualty of the knee jerk scheme change. He was just as much of a poor fit as Carr and Claiborne became.
The weakside linebacker in the scheme is just as key as the three technique tackle to the overall success of the defense. It is the position that Derrick Brooks played in Tampa and that Briggs played in Chicago. His level of play was a big reason why the defense was broken.
The tentativeness people see is undoubtedly due to him mentally struggling with the assignments. If you are not sure what you are doing, you play so. If you are thinking too much, you are going to take false steps and look like you want nothing to do with the action.
He had a really bad season. It started when he dropped the interception in Kansas City, got worse when Danny Woodhead abused him and benching him for Ernie Sims did not help his confidence much either. He just looked like he mentally checked out after that point. The Saints game was horrific.