If you want to see all 32 teams, click on thishttp://bleacherreport.com/articles/2705056-power-ranking-all-32-nfl-defenses-post-draft.
Otherwise, I copied & pasted the top 5.
5. New York Giants
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Matt Ludtke/Associated Press
Defensive Coordinator: Steve Spagnuolo
Base Defense: 4-3
It's very rare for a team to go from having a bottom-five defense one year to a top-five defense the following year, but that's exactly what the Giants did in 2016. After giving up more than 27 points and 420 yards per game in 2015, the New York Giants rebuilt their defense and had one of the more dominant units in the league in 2016. They finished second in points allowed, giving up fewer than 18 points per game.
What was even more impressive was how the Giants were the only team in the league able to stop the Cowboys offense. In two meetings against Dallas, the Cowboys were held to just 26 points as the Giants won both matchups.
Last season, the Giants added a dominant nose tackle in Damon "Snacks" Harrison to clog the middle so that Jason Pierre-Paul and newly-signed end Olivier Vernon could scream off the edges and get to the quarterback.
Heading into 2017, the defense is mostly unchanged. The only notable loss is Johnathan Hankins, but his replacement was selected in the second round with Dalvin Tomlinson from Alabama.
This is a young defense, especially in the secondary, and it could improve drastically if the Giants can get better play from their linebackers. The Giants should be in the top five in points allowed again in 2017.
4. New England Patriots
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Winslow Townson/Associated Press
Defensive Coordinator: Matt Patricia
Base Defense: 4-3
After finishing as the No. 1 defense in 2016 in points allowed, the Patriots added one of the best free agents on the market in Stephon Gilmore. Not only did they add a talented cornerback to pair with Malcolm Butler, they were also able to bring in Kony Ealy via trade and Derek Rivers through the draft. Already possessing one of the best defenses in the NFL, the Patriots didn't stop adding talent.
What makes the Patriots defense so special is that it is able to adapt and adjust to whatever offense its face. When facing a passing attack, the Patriots have enough depth in their secondary to match their opponents' weapons. If they are playing a power-running team, they have enough beef in the front seven to shut down even the best rushing attacks.
The Patriots don't have one single player who stands out amongst the rest, but their defense collectively is one of the best. They don't have an elite pass rush, nor do they take the ball away at an outstanding rate. But they know how to shut down even the best offenses in the NFL. The Patriots allowed just 15.6 points per game in 2016 and have only improved their defense heading into 2017.
3. Denver Broncos
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Mark Zaleski/Associated Press
Defensive Coordinator: Joe Woods
Base Defense: 3-4
After a dominant run in 2015 led to the Broncos winning the Super Bowl, the Denver defense fell off some in 2016. They finished fourth in points per game and first in passing yards allowed per game, but the team had the 28th-ranked run defense. Opponents ran for an average of 130 yards per game.
Adjusting to life after Wade Phillips will be tough for the Broncos, but they are still loaded with talent on defense. Led by Von Miller, the Broncos should be able to pressure the quarterback as well as any team in the league. If the team's offense can better control the clock, the defense won't be run on as much as it was in 2016. The Broncos still have one of the best defenses in the entire NFL.
2. Houston Texans
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Eric Christian Smith/Associated Press
Defensive Coordinator: Mike Vrabel
Base Defense: 3-4
Despite losing their leader in J.J. Watt for most of the season due to a back injury, the Texans still finished 11th in points allowed in 2016. But what's more impressive is that they finished first in total yards allowed, giving up just 301 per game.
With Watt returning and the team adding Zach Cunningham in the draft, the Texans have a realistic chance to finish with the best defense in the league. They will need to adjust to losing cornerback A.J. Bouye in free agency, but the team has the best group of pass-rushers in the entire league. If Watt is able to return to his usual self, he and Jadeveon Clowney will be terrifying together on the field. This is one of the best defenses in the entire NFL.
1. Seattle Seahawks
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David Goldman/Associated Press
Defensive Coordinator: Kris Richard
Base Defense: 4-3
While there were rumors that Richard Sherman was on the trading block this offseason, it is unlikely the team would move him after the draft. And with him staying, the Seahawks return one of the best defenses in the NFL.
Despite losing Earl Thomas to a season-ending injury in the middle of the year, Seattle still finished top five in points and yards allowed in 2016. The Seahawks finished tied for third in sacks with 42 and were one of the league's most dominant units.
However, the loss of Thomas due to a broken leg exposed how much the team truly relies on their playmaking center fielder. The Seahawks focused on adding depth to their defensive backs in the draft this year, selecting three safeties and one cornerback, possibly as further insurance against another Thomas injury.
Thomas is the leader of the defense and the heart and soul of everything they do on every snap. When he's on the field, they are the best defense in the NFL.
Along with grabbing four defensive backs in the draft, the Seahawks added Malik McDowell at the top of the second round. McDowell is a 20-year-old star who needs to be motivated to play at a high level. With the Seahawks and expert motivator Pete Carroll, he will be a fantastic addition for the team.
As long as their stars stay healthy, the Seahawks are a lock to finish in the top five again in points and yards allowed per game.