Madden 21 has multiple great defensive teams that you can use in gameplay. However, you can't solely choose your team based on their defensive rating. The best defensive teams have the best defensive playbooks, and the team with the best defensive playbook is...
The Baltimore Ravens.
Who Has the Best Defensive Playbook in Madden 21?
The Ravens boast a 86 defense, which is not even the best-rated defense in the game. Both the 49ers and Bears have higher rated defenses than the Ravens, yet they don't have better playbooks.
Patrick Queen is a top linebacker in the league, and the Ravens playbook uses him perfectly. They have the perfect scheme to use him as both a blitzer and in man coverage.
Zone defense is often used in online games, but the Ravens playbook implements man coverage very often. Their man coverage works very well because of their great safety play.
The safeties and linebackers ability to cover receivers and tight ends allow for the team to blitz while in man coverage. An especially good blitz option from their playbook is the cornerback blitz. If the opponent does not do a quick slant or short route, it will be a sack or a loss of yards if it's a run play.
The Ravens have by far the best defensive playbook on the game. They also have great players in all phases of the defense which makes it very hard to score on them.