With the 2015 NFL regular season now in the books, we can look at final numbers -- we don't have to use "on pace for," "if he continues," or other similar midseason vocabulary.

And with that, we can start analyzing teams a little deeper, showing how they improved -- or dropped off -- from one year to the next.

Using our Net Expected Points (NEP) metric, which evaluates players and teams based on how they performed versus expectation, we can rank the NFL's defenses. For this article, I compared all 32 teams between 2014 and 2015 in schedule-adjusted NEP and found the five teams whose rank improved the most this season.

Which team defense do you think took the biggest forward in 2015? Will it be able to keep it up next season?