...but only because he had fewer valid reasons / excuses.
I understand that in 2014, our defensive lineup was closer to a medical infirmary roster, rather than a usable defense. I gave him a mulligan because of that.
In 2015, he had a pretty healthy lineup, and most folks were willing to overlook things, given that we did make it to a big time bowl game.
In 2016, he kept trying to fit square pegs in round holes, and vice versa, *still* not realizing that his defensive scheme was a terrible fit for ND's personnel. A decent DC should know when things aren't working, and change strategies accordingly.
As for Gary Darnell, I gave him a bit of a mulligan in 1990 because the secondary stank, and we even resorted to converting RB's into serviceable defensive backs. It wasn't easy replacing three NFL draft picks (Smagala, Terrell, and Francisco), especially when their replacements weren't nearly ready for the job.
Todd Lyght was hampered throughout most of the year with a nasty deep thigh bruise, Rod Smith was playing out of position (he was a better safety, and not a cornerback), Greg Davis was mediocre, at best, and George Poorman, well, was a very poor defensive back, period. If anything, Lou ended up making Poorman the 4th string quarterback, to keep him out of the way...
Darnell still had to accept some responsibility, though... When he made the DB's play 10 yards off the receivers on a constant basis, it's no wonder that various quarterbacks had field days against us. I still remember Tony Sacca carving up our secondary, and having his epiphany game against us in 1990.
In 1991, Darnell's defensive squad was pretty much gutted. The guy we were counting on to anchor the defensive line, George "Boo" Williams, was kicked off the team for marijuana use, and having to replace almost all of the front seven with newcomers would have made the Augean Stables look easy in comparison. As good as Bryant Young ended up being for us (one of the best of all time), having him play nose tackle at a scant 250 pounds against well-developed offensive linemen wasn't a very good scenario. He did manage to hold his own, but was still 25 lbs underweight at the time. Losing him for a couple of games due to a cheap AIr Force player's dive at his knee didn't help things either.
The only ones who were ready to hit the ground running, was Eric Jones, as he was our best pass rusher, and Devon MacDonald. Unfortunately, we lost Jones due to a cheap shot by an Air Force player, who dove at his ankles full blast, while another blocker was engaging him.
Jim Flannigan was struggling to keep his weight down as a linebacker. I'm glad that they did finally shift him to DT, where he truly belonged, as he ended up being a fine one for us.
Brian "Hambone" Hamilton wasn't ready yet, neither was Ollie Gibson. Again, both were excellent players afterwards, but 1991 wasn't the right time for them.