Evaluating the top defensive units in the NHL isn't as cut and dry as determining the best offenses, as defensive play can be more difficult to quantify. Goaltending, while technically an element of defense, can skew true prowess and make it seem as though an average club is better than the underlying numbers truly indicate.

The New York Islanders are a prime example. They allowed the fewest goals in the NHL last season, but a closer look at their metrics shows that they placed near the middle or bottom of the pack at suppressing shots, preventing scoring chances, and killing penalties, and that the defense was bailed out by outstanding goaltending from Robin Lehner and Thomas Greiss.

We focused on which groups are the best at limiting opportunities and stifling opposing offenses.

Here are the top five defenses in the league for 2019-20, based on last season's performance, the personnel, and how each stack up for the upcoming campaign: