Their defense is better than their norm, significantly better.
Overall, their FEI rank is 15th, while ND is 23rd. (For FEI, all drives are filtered to eliminate first-half clock-kills and end-of-game garbage drives and scores. A scoring rate analysis of the remaining possessions then determines the baseline possession efficiency expectations against which each team is measured. A team is rewarded for playing well against good teams, win or lose, and is punished more severely for playing poorly against bad teams than it is rewarded for playing well against bad teams.)
In 2017, Navy ended at 38th (ND won the game by 7, back and forth game where ND scored late in the third and early in the fourth to get the lead).
In 2016, Navy ended at 33rd and beat ND that year.
On paper this is their best team since 2015, when they went 10-2. That year, ND beat them 41-24, but that game was marred by two Navy fumbles inside their own 25 that ended up being the difference. Without those, that game would have been a dogfight. I fully expect this week to be no different.