Jim Knowles was introduced as Penn State's defensive coordinator on Tuesday. Here's what he said about leaving Ohio State football.

Jim Knowles' defense is not static and is certainly malleable to suggestions, but even a veteran coach has a breaking point with directives.  The coordinator reached his limit after three years at Ohio State,

The departure of defensive coordinator Jim Knowles adds a challenge for Ohio State, which was already dealing with heavy roster turnover on defense.