Tackling was sloppy, assignments were missed, overpursuit was common, and the defensive line rarely, if ever, got any kind of decent penetration.
Hell, special teams cost us the margin of victory in at least 3-4 games last year, and almost ended up costing us the Miami game as well. That could easily have been a 3-9 season, despite the fact that these are all Brian Kelly's players that he developed throughout the years, in his scheme, and using his methods.
If he can't figure it out in 2017 (by getting at least a 10 win season), then he's getting the heave-ho.